REMEDIAL INVESTIGATION AND FEASIBILITY STUDY WORK … RI...AECOM has prepared this Remedial...

REMEDIAL INVESTIGATION AND FEASIBILITY STUDY WORK PLAN (DRAFT)

BENNING ROAD FACILITY

3400 BENNING ROAD, N.E.

WASHINGTON, DC 20019

PREPARED FOR:

Pepco and Pepco Energy Services

701 9th

Street, NW

Washington, DC 20068

PREPARED BY:

AECOM

8320 Guilford Road, Suite L

Columbia, MD 21046

July 2012

REMEDIAL INVESTIGATION AND FEASIBILITY STUDY WORK PLAN (DRAFT) Benning Road Facility

3400 Benning Road, N.E.

Washington, DC 20019

________________________________ _________________________________ Compiled By: Compiled By: Sean Crouch, E.I.T. Kevin Yue, E.I.T. Environmental Engineer, AECOM Environmental Engineer, AECOM

_________________________________ _________________________________ Reviewed By: Reviewed By: Ravi Damera, P.E., BCEE For: John Bleiler

Senior Project Manager, AECOM Senior Technical Reviewer, AECOM

Benning Road Facility DRAFT July 2012 RI/FS Work Plan

Contents

1 Introduction ....................................................................................................................... 1

1.1 Work Plan Purpose and Scope ...............................................................................................2

1.2 Work Plan Organization ..........................................................................................................2

2 Site Background and Setting ........................................................................................... 4

2.1 Site Description ........................................................................................................................4

2.2 Area Description ......................................................................................................................7

2.2.1 General Land Use and Demography .......................................................................7

2.3 Geology ....................................................................................................................................8

2.3.1 Regional Geology .....................................................................................................8

2.3.2 Site Specific Geology ...............................................................................................9

2.4 Hydrogeology ........................................................................................................................ 10

2.4.1 Regional Hydrogeology ......................................................................................... 10

2.4.2 Site Specific Hydrogeology ................................................................................... 10

2.5 Surface Water Hydrology and Watershed Characteristics ................................................. 10

2.6 Historical Removal Actions and Investigations .................................................................... 11

2.6.1 Regional Assessment of Anacostia River and Suspected Area-Wide Sources of Impact

................................................................................................................................ 12

3 Conceptual Site Model ................................................................................................... 20

3.1 Landside ............................................................................................................................... 20

3.2 Waterside .............................................................................................................................. 22

4 Work Plan Rationale ....................................................................................................... 24

4.1 Data Quality Objectives ........................................................................................................ 24

4.2 Work Plan Approach............................................................................................................. 25

4.2.1 Landside Investigation ........................................................................................... 26

4.2.2 Waterside Investigation ......................................................................................... 26

5 RI/FS Tasks ...................................................................................................................... 28

5.1 Project Planning .................................................................................................................... 28

5.2 Field Investigation Activities ................................................................................................. 28

5.2.1 Landside Investigation ........................................................................................... 28


5.2.2 Waterside Investigation ......................................................................................... 33

5.2.3 Investigation-Derived Waste (IDW) Management ................................................ 39

5.3 Data Evaluation and Validation ............................................................................................ 40

5.3.1 Data Management ................................................................................................. 43

5.3.2 Field Data Collection and Transmission ............................................................... 43

5.3.3 Data Review........................................................................................................... 43

5.3.4 Project Database ................................................................................................... 43

5.4 Risk Analysis......................................................................................................................... 43

5.4.1 Human Health Risk Assessment .......................................................................... 44

5.4.2 Ecological Risk Assessment ................................................................................. 46

5.5 Remedial Investigation Report ............................................................................................. 47

5.6 Feasibility Study .................................................................................................................... 47

5.6.1 Identification of Remediation Requirements and Establishment of RAOs .......... 48

5.6.2 Development and Screening of Remedial Alternatives ........................................ 48

5.6.3 Treatability Studies ................................................................................................ 48

5.6.4 Detailed Analysis of Alternatives ........................................................................... 49

5.6.5 Feasibility Study Report ........................................................................................ 49

5.6.6 Regulatory Review and Public Comment ............................................................. 49

6 Project Organization ....................................................................................................... 50

7 Schedule .......................................................................................................................... 54

8 References ....................................................................................................................... 55

List of Tables

Table 1: Historical Removal Actions and Investigations Table 2: Target Areas Table 3: Landside Data Quality Objectives Table 4: Waterside Data Quality Objectives Table 5: Landside Data Collection Program Table 6: Waterside Data Collection Program Table 7: Project Team


List of Figures

Figure 1: Site Location Map Figure 2: Site Plan and Investigation Areas Figure 3: RI/FS Process Figure 4: Site Vicinity Map Figure 5: Target Areas Figure 6: Regional Geologic Profile Figure 7: Historical Soil Borings Figure 8: Geologic Cross Sections Figure 9: Preliminary Conceptual Site Model Figure 10: Proposed Surface Soil Sample and ERI Transect Locations Figure 11: Sediment Sample Locations Figure 12: Benning Road RI/FS Project Timeline

Appendices

Appendix A: USGS Lithologic Section along the Anacostia River Appendix B: Anacostia River Watershed Maps Appendix C: Existing Anacostia River Chemical Data based on NOAA Database Appendix D: Human Health Risk Assessment Work Plan Appendix E: Ecological Risk Assessment Work Plan Appendix F: Remedial Investigation Report Outline


List of Acronyms

ANS Academy of Natural Sciences ASTM American Society for Testing and Materials AST Aboveground Storage Tank AVS Acid Volatile Sulfide AWTA Anacostia Watershed Toxics Alliance BTAG Biological Technical Assistance Group CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CIP Community Involvement Plan cm/yr Centimeter per Year COC Constituent of Concern CLP Contract Laboratory Program COPC Constituent of Potential Concern CSF Complete Sample Delivery Group File CSM Conceptual Site Model CSO Combined Sewer Overflow DC District of Columbia DCRA Department of Consumer and Regulatory Affairs DCWASA District of Columbia Water and Sewer Authority DDOE District Department of the Environment DGPS Differential GPS DNAPL Dense Non-Aqueous Phase Liquid DO Dissolved Oxygen DOD Department of Defense DQO Data Quality Objectives DPT Direct Push Technolgy EDD Electronic Data Deliverables EDR Environmental Data Resources EPC Exposure Point Concentration ERA Ecological Risk Assessment ERI Electrical Resistivity Imaging ESA Environmental Site Assessment ESTCP Environmental Security Technology Certification Program FS Feasibility Study FSP Field Sampling Plan ft bgs Feet Below Ground Surface GC/MS Gas Chromatography/Mass Spectrometry GIS Geographic Information System GPS Global Positioning System GSA General Services Administration HASP Health and Safety Plan HHRA Human Health Risk Assessment HSA Hollow Stem Auger ICP Inductively Coupled Plasma ICPMS Inductively Coupled Plasma-Mass Spectrometry IDW Investigation Derived Waste


KPN Kenilworth Park North KPS Kenilworth Park South LNAPL Light Non-Aqueous Phase Liquid mg/kg Milligrams per Kilogram mg/L Milligrams per Liter MLLW Mean Low Low Water MS/MSD Matrix Spike/Matrix Spike Duplicate MW Megawatt MWCOG Metropolitan Washington Council of Governments NOAA National Oceanic and Atmospheric Administration NPL National Priority List NPS National Park Service NPDES National Pollutant Discharge Elimination System NRDA Natural Resource Damage Assessment NTU Nephelometric Turbidity Units NWP Nationwide Permit OSWER U.S. EPA Office of Solid Waste and Emergency Response PA Preliminary Assessment PAH Polycyclic Aromatic Hydrocarbon PCB Polychlorinated Biphenyls PES Pepco Energy Services PID Photoionization Detector PPE Personal Protective Equipment ppm Parts per Million PRG Preliminary Remediation Goal PVC Polyvinyl Chloride QAPP Quality Assurance Project Plan QA/QC Quality Assurance/ Quality Control RAO Remedial Action Objectives RAS Routine Analytical Services RCRA Resource Conservation and Recovery Act RI Remedial Investigation RI/FS Remedial Investigation/Feasbility Study RPD Relative Percent Difference SAP Sampling and Analysis Plan SDG Sample Data Group SEM Simultaneously Extractable Metals SEFC Southeast Federal Center SI Site Inspection SOP Standard Operating Procedure SOW Scope of Work SPT Standard Penetration Test SQG Sediment Quality Guidelines SVOC Semi-Volatile Organic Compound TOC Total Organic Carbon TPH Total Petroleum Hydrocarbons TRV Toxicity Reference Values TSCA Toxic Substances Control Act µg/kg Microgram per Kilogram µmhos/cm Micromhos per Centimeter


USACE United States Army Corps of Engineers USCG United States Coast Guard USCS Unified Soil Classification System USEPA United States Environmental Protection Agency USGS United States Geological Survey UST Underground Storage Tank VOC Volatile Organic Compound WGL Washington Gas Light WMATA Washington Metropolitan Area Transit Authority WNY Washington Navy Yard XRF X-Ray Fluorescence


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1 Introduction

AECOM has prepared this Remedial Investigation and Feasibility Study (RI/FS) Work Plan on behalf of Potomac

Electric Power Company (Pepco) and Pepco Energy Services, Inc. (collectively “Pepco”) to describe the overall

technical approach of the RI/FS at Pepco’s Benning Road facility (the Site), located at 3400 Benning Road NE,

Washington, DC, and a segment of the Anacostia River (the River) adjacent to the Site. The general site location

is shown on Figure 1. Together, the Site and the adjacent segment of the River are referred to herein as the

“Study Area”. Pepco has agreed to perform the RI/FS pursuant to a consent decree that was entered by the U.S.

District Court for the District of Columbia on December 1, 2011 (the Consent Decree). The Consent Decree

documents an agreement between Pepco and the District of Columbia (District) which is part of the District’s

larger effort to address contamination in and along the lower Anacostia River.

The purpose of the RI/FS described herein is to (a) characterize environmental conditions within the Study Area,

(b) investigate whether and to what extent past or current conditions at the Site have caused or contributed to

contamination of the River, (c) assess current and potential risk to human health and the environment posed by

conditions within the Study Area, and (d) develop and evaluate potential remedial actions. As described later in

this document, the Study Area consists of a “landside” component that will focus on the Site itself, and a

“waterside” component that will focus on the shoreline and sediments in the segment of the river adjacent to and

immediately downstream of the Site. The landside and waterside areas of investigation are depicted in Figure 2.

The areas of investigation may be further adjusted or expanded during the course of the RI as warranted based

on the findings of the investigation.

The RI/FS will be performed in accordance with the United States Environmental Protection Agency’s (USEPA)

Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA, Office of Solid Waste

and Emergency Response (OWSER) Directive 9355.3-01, dated October 1988, and other applicable USEPA and

District Department of the Environment (DDOE) guidance documents. A generalized RI/FS process is shown in

Figure 3. Pepco previously submitted the RI/FS Scope of Work (SOW) to DDOE and revised it to address

comments from DDOE and the public. Final approval for the SOW was provided by DDOE on April 18, 2012.

The approved SOW serves as a blue print for this Work Plan. Pepco also prepared a separate Community

Involvement Plan (CIP), which was revised to address DDOE and public comments, and was approved by DDOE

on June 18, 2012, to describe Pepco’s community outreach activities during the RI/FS process.


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1.1 Work Plan Purpose and Scope

The purpose of this Work Plan is to review existing data, develop a Conceptual Site Model (CSM), identify data

gaps, design a data collection program to address the identified data gaps, and document the planned RI/FS

activities in accordance with the previously-approved SOW. The Work Plan also presents information on project

organization and schedule.

Field work activities described in this Work Plan will be performed in accordance with a Health and Safety Plan

(HASP) and a Sampling and Analysis Plan (SAP) prepared in conjunction with the Work Plan. The HASP will

specify necessary procedures to ensure safety of Site workers during the investigation activities for both the

landside and waterside investigations. The SAP consists of two parts: (a) a Field Sampling Plan (FSP) that

provides detailed guidance for all field work by defining in detail the sampling locations and the sampling and data

gathering methods to be used; and (b) a Quality Assurance Project Plan (QAPP) that describes quality assurance

and quality control protocols necessary to achieve Data Quality Objectives (DQOs) dictated by the intended use

of the data. The HASP and SAP documents are being provided under separate cover.

DDOE will make the Work Plan (including CSM), HASP and SAP available for public review for at least 30 days

by posting on the DDOE website prior to granting its approval. Upon approval of this Work Plan by DDOE (after

consideration of public comments), Pepco will implement the activities outlined in this document. The areas of

investigation and sampling locations may be adjusted or expanded (with DDOE approval) during the course of the

RI as warranted based on the findings of the investigation.

1.2 Work Plan Organization

This RI/FS Work Plan is organized into the following eight sections:

Section 1 - Introduction

Section 2 - Site Background and Setting

Section 3 - Conceptual Site Model

Section 4 - Work Plan Rationale

Section 5 - RI/FS Tasks

Section 6 - Project Orgainzation


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Section 7 - Schedule

Section 8 - References

Figures, tables, and appendices are provided as stand-alone sections following Section 8.


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2 Site Background and Setting

The 77-acre Site is bordered by a District of Columbia Solid Waste Transfer Station to the north,

Kenilworth Maintenance Yard (owned by the National Park Service, NPS) to the northwest, the Anacostia

River to the west, Benning Road to the south and residential areas to the east and south (across Benning

Road). Most of the Site is comprised of the Benning Service Center, which involves activities related to

construction, operation and maintenance of Pepco’s electric power transmission and distribution system

serving the Washington, DC area. The Service Center accommodates more than 700 Pepco employees

responsible for maintenance and construction of Pepco’s electric transmission and distribution system;

system engineering; vehicle fleet maintenance and refueling; and central warehousing for materials,

supplies and equipment. The Site is also the location of the Benning Road Power Plant, which is

scheduled to be shut down in 2012.

The Site is one of several properties along the River that are suspected sources of contamination (Figure

4). There have been five instances between 1985 and 2003 in which materials containing polychlorinated

biphenyls (PCBs) were released at the Site. In each case, Pepco promptly cleaned up the releases in

accordance with applicable legal requirements. A summary of historical environmental investigations and

response actions conducted on the Site by Pepco and the USEPA is presented in Table 1. Nonetheless,

it is suspected that these releases, and possibly other historical operations or activities at the Site, may

have contributed to contamination in the river. In particular, a Site Inspection (SI) conducted for the

USEPA in 2008 linked PCBs and inorganic constituents detected in Anacostia River sediments to

potential historical discharges from the Site. (The results of this Site Inspection are referred to herein as

USEPA 2009 SI Report.) The USEPA SI Report also stated that currently the Site is properly managed

and that any spills or leaks of hazardous substances are quickly addressed and, if necessary, properly

remediated (USEPA, 2009).

2.1 Site Description

The geographic coordinates for the approximate center of the Site are 38.898 north Latitude and 76.959

west Longitude. A Site Plan is provided as Figure 5. As of June 1, 2012, operations at the Benning Power

Plant have ceased as announced by Pepco Energy Services (PES) which has owned and operated the

power plant since 2000. The power plant is located on the westernmost portion of the Benning Service

Center site, where it occupies approximately 25 percent of the facility's 77 acres. Preparations for closing


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the power plant have been underway since 2007. Following the closure, the plant area will be cleaned,

secured, and maintained in accordance with District of Columbia and Federal environmental regulations.

The power plant was built in 1906, and provided Pepco's first system-wide electricity supply to the District of

Columbia and nearby Maryland suburbs. Over the years, the power plant has operated and subsequently

retired several different generating units, reflecting advances in technology and operating on different types

of fuel. Only two oil-fired steam turbine units operated at the power plant in the recent past. Installed in

1968 and 1972, together they provide 550 megawatts (MW) of electricity - enough to meet the needs of

around 180,000 homes - during periods of peak electricity demand. Designed to operate a limited number

of days each year, these units have operated an average of 10 to 15 days annually. Structures associated

with the power plant include the generating station, cooling towers, three aboveground storage tanks (ASTs)

and storage buildings. The three ASTs are surrounded by secondary containment dikes. As of the writing

of this work plan, AST #1 was emptied and AST #2 is being pumped down. This will be followed by draining

of AST #3. Once the #4 fuel oil contents are removed, all tanks will be cleaned. The power plant closure

will include removal of the cooling tower and AST structures.

The Service Center occupies the largest part of the property, and accommodates more than 700 Pepco

employees. Service Center employees work in maintenance and construction of Pepco’s electric

transmission and distribution system; system engineering; vehicle fleet maintenance and refueling; and

central warehouses for all the materials, supplies and equipment needed to operate the Pepco electrical

distribution system.

The Site is completely surrounded by a fence with two guarded entrances. The guard shacks are staffed

24 hours a day, 7 days a week. Three active substations are located on the Site, two in the eastern

portion (Substation #41 and Substation #7) and one in the western portion (Substation #45). To the south

of the substations is a large asphalt-covered Pepco employee parking lot. To the south of this area are

railroad tracks and Buildings 56, 57, and the transformer staging area. These areas are used for activities

associated with processing used electrical equipment and associated materials brought to the Site for

reconditioning, recycling or disposal. The center of the Site is occupied by buildings used for office

space, vehicle maintenance, equipment repair shops and storage of hazardous waste and materials.

Areas located outside of the buildings are used for new equipment storage and also temporary storage of

used electrical equipment prior to disposal.

There are three active underground storage tanks (USTs) at the Site. One is a 15,000-gallon double-

walled steel and fiberglass tank installed in 1988 to hold new transformer oil. A 20,000-gallon fiberglass

tank, installed in 1975, contains gasoline. A 20,000-gallon double-walled tank, installed in 1991, holds


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diesel fuel. All tanks have leak detection monitoring devices which test the tanks and aboveground piping

for leaks on a monthly basis. These tanks are operated in compliance with the District’s UST regulations.

A separate 20,000-gallon epoxy-coated steel tank, installed in 1979 and used to store gasoline, was

recently taken out of service and is scheduled for removal in August 2012. DDOE has been notified of

the tank removal. Please refer to Table 2 for further details regarding the USTs and Figure 5 for the

locations.

The majority of the Site is covered by impervious material such as concrete or asphalt. Active storage

areas not covered in impervious material are covered in gravel. One of the gravel-covered areas is

located in the western portion of the site, directly south of the cooling towers. This area was used at one

time for the storage of coal when the power plant used coal to generate electricity. Later, this area was

used to dewater sludge cleaned out from the basins located underneath the cooling towers. The area is

no longer used for either purpose. Railroad tracks enter the site from the south and run to the north. The

tracks were formerly used to transport coal to the power plant and are no longer active.

Storm water runoff from the facility is conveyed through a drain system (Figure 5) and is discharged to

the River and City storm drains at various outfalls under an NPDES permit (DC0000094). Two outfalls

(Outfall 013 and Outfall 101) discharge to the River. The majority of the runoff from the facility is

conveyed through a 48-inch concrete pipe to the 54-inch pipe to the River via Outfall 013. In addition,

Outfall 013 was also permitted to receive cooling tower blow down and cooling tower basin wash water

when the cooling towers operated. These towers are no longer operational, as Pepco ceased the

operations at Benning Road Power Plant effective June 1, 2012. Outfall 101 includes discharges from

storm water runoff, storm water collected in transformer secondary containment basins, and roadways

and landscaping in the southwest corner of the property. Other outfalls, capturing primarily roadway

runoff, are discharged to the District municipal storm drain system.

Outfalls discharging to the Anacostia River are sampled on a quarterly basis under the National Pollutant

Discharge Elimination System (NPDES) permit. The analytical parameters include the following:

pH;

Oil and grease;

Iron;

Cadmium;

Copper;

Lead;

Nickel;


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Zinc; and

PCBs (aroclor-1242, aroclor-1254 and aroclor-1260).

Among the discharge locations included in the routine sampling program, are the storm sewers

determined potentially at risk for receiving PCB contaminated runoff. According to the USEPA 2009 SI

Report, no NPDES violations have been recorded for the Site and USEPA has reported that no PCBs

have been detected in the NPDES compliance samples. A review of Discharge Monitoring Reports

(DMRs) from the first quarter of 2012 indicates no excursions for PCBs and excursions of copper, zinc

and iron. Pepco is implementing a Total Maximum Daily Load (TMDL) Implementation Plan approved by

the USEPA to identify and reduce the sources of metals in storm water discharges from the facility. In

addition, Pepco also analyzes for PCB congeners as required by the NPDES permit, for monitoring

purposes only.

2.2 Area Description

2.2.1 General Land Use and Demography

The Site is located in Ward 7 in the District of Columbia, within the 20019 zip code. Ward 7 is typified by

single-family homes and parks. It is home to a number of Civil War fort sites that have since been turned

into parkland, including Fort Mahan Park, Fort Davis Park, Fort Chaplin Park and Fort Dupont Park. Ward

7 is also home to green spaces such as Kenilworth Aquatic Gardens, Watts Branch Park, Anacostia River

Park and Kingman Island.

Ward 7 also has an extensive waterfront along the Anacostia River with riverfront neighborhoods. River

Terrace, Mayfair and Eastland Gardens abut the east side of the river, while Kingman Park sits to the

west. The River Terrace, Parkside and Benning neighborhoods are engaged and organized

communities. Ward 7 is represented by Councilmember Yvette Alexander and is home to the Mayor of

the District of Columbia, Vincent C. Gray.

This area is primarily urban with the Anacostia River bordering the area to the west. The Anacostia

Freeway is the main north-south highway and East Capitol Street NE is the main east-west highway.

Transportation in the vicinity of the Site takes the form of light rail or motorized vehicles. The Washington

Metropolitan Area Transit Authority (WMATA) operates the light rail system in Washington, DC (known as

Metrorail). The Minnesota Avenue Metrorail Station is located immediately to the east of the Site.

Approximately 19% of the population in the 20019 zip code uses Metrorail to commute to and from work,

with an average of 3,274 people using the Minnesota Avenue Station per day. A large percentage of the

local residents use automobiles, either singly or in carpools, to commute to and from work.


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Minnesota Avenue in the vicinity of the Site is zoned as commercial. In addition, a commercial light

manufacturing corridor exists along the Kenilworth Ave/Metrorail tracks. Property along Benning Road is

zoned sporadically as commercial. All other surrounding areas are largely residential. Most of the

houses in the area were built between 1940 and 1969. The majority of the housing units are either

single-family detached or single-family attached units. There are three high schools, 21 public

primary/middle schools, and five private primary/middle schools within the boundaries of zip code 20019.

Of the schools reported being within the 20019 zip code, four are located within a 0.25-mile radius of the

boundary of the Site: Thomas Elementary School, Cesar Chavez Middle and High School, Benning

Elementary School, and River Terrace Elementary School (Google Earth).

According to the Final USEPA SI Report dated June 2009, there are no drinking water intakes located

within 15 miles of the Site. The District of Columbia Water and Sewer Authority (DCWASA) provides

drinking water to the surrounding area by drawing raw water from intakes located at Great Falls and Little

Falls on the Potomac River, upstream from the confluence of the Potomac River with the Anacostia River

(http://www.dcwater.com/about/facilities.cfm).

Based on a review of the Environmental Data Resources, Inc. (EDR) Report provided by Greenhorne and

O’Mara, Inc. dated September 2009, no water supply wells are located within 0.5-mile of the Site. One

United States Geological Survey (USGS) monitoring well was identified 500 feet northwest of the Site and

adjacent to the Anacostia River. Upon further review, this monitoring well appears to be the USGS Soil

Boring DCHP01 discussed in Section 2.3.

2.3 Geology

2.3.1 Regional Geology

The facility is located within the Coastal Plain Physiographic Province, which is characterized by eastward

thickening sequences of sedimentary deposits. The western limit of the Coastal Plain Province is

commonly referred to as the Fall Line, where the older crystalline rocks (bedrock) of the Piedmont

Physiographic Province begin to dip to the southeast beneath the relatively younger sediments of the

Coastal Plain. The Fall Line is located approximately five miles west of the Site.

The Coastal Plain consists of an eastward-thickening wedge of unconsolidated sedimentary deposits

ranging in geologic age from Cretaceous to Recent. These unconsolidated sediments consist of gravels,

sands, silts, and clays that have been deposited upon the consolidated crystalline bedrock which slopes

towards the southeast. Many different depositional environments existed during the formation of the

Coastal Plain sediments. Glacially influenced periods of erosion and deposition, fluvial (river) processes,

http://www.dcwater.com/about/facilities.cfm


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and structural deformations of the sedimentary deposits have all played a part in the evolution of the

Coastal Plain. As a result of these processes, the presence, thickness, and lateral continuity of these

sedimentary deposits in the Coastal Plain are highly variable. A generalized regional geologic profile has

been included as Figure 6.

2.3.2 Site Specific Geology

Based upon a review of available historical reports (Section 8), the soils underneath the Site consist

primarily of (from shallowest to deepest): artificial fill material; Patapsco Formation; Arundel Clay unit; and

the Patuxent Formation. The Patuxent Formation overlies the crystalline bedrock.

The artificial fill material at the Site primarily consists of infrastructure (utilities and structures), historical fill

material used to level the site, process related fill, and relatively impermeable pavement (asphalt and

concrete). Fill material thickness at the Site is as much as ten feet in some areas with the exception of

the vicinity of the former sludge dewatering area, where fill thicknesses ranged from 14 to 17 feet.

The Patapsco Formation is typically described as a thick maroon clay, with sand and clay of various

colors. Underneath the Patapsco Formation is the Arundel Clay which generally consists of thick dark

grey clay. Arundel Clay is a distinct regional confining feature with very low permeability. The thickness

of the Arundel Clay varies, but has been observed to be as much as 100 feet thick (USGS, 2002).

Beneath the Arundel Clay are the unconsolidated gravels, sands, and clays of the Patuxent Formation.

The top of the Patuxent Formation has been reported to be located at approximately 125 to 180 feet

below ground surface (ft bgs) in nearby environmental assessments (NPS, 2008). The Crystalline

bedrock underneath the Patuxent Formation is located at approximately 400 feet beneath the Site.

AECOM has reviewed and compiled information from 32 geotechnical borings completed by Pepco on the

Site with the deepest boring (GEO B-9) drilled to a depth of 81 ft bgs. Approximate locations of these

historical soil borings are shown on Figure 7. Information from these borings was used to generate

generalized geologic cross sections, A-A’ and B-B’ (Figure 8). The cross sections indicate an upper and

a lower water bearing zone separated by a clay unit within the Patapsco formation. This information

appears to be consistent with the findings of United States Geological Survey (USGS), Lithologic Coring

Program Boring DCHP01 (Appendix A). Based on a review of the borehole logs available for the site,

the Arundel Clay is located approximately 42 to 73 feet beneath the Site.


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2.4 Hydrogeology

2.4.1 Regional Hydrogeology

Based on the literature reviews and information from adjacent sites, aquifers underneath the Site consist

of saturated sand layers within the Patapsco and Patuxent Formation and include (from shallowest to

deepest): the Upper Patapsco Aquifer; the Lower Patapsco Aquifer; the Upper Patuxent Aquifer; and the

Lower Patuxent Aquifer. The Lower Patapsco and upper Patuxent Aquifers are separated by the thick

Arundel Clay unit. The Arundel clay has very low conductivity and acts as a regional aquitard between

the Patapsco and Patuxent Formations. The Patuxent Aquifer, located beneath the Arundel Clay, flows

under confined conditions towards the east (DC Water Resources, 1993).

2.4.2 Site Specific Hydrogeology

Based on review of the lithologic logs available for the Site, the Arundel Clay is located approximately 42

to 73 ft bgs beneath the Site. The information contained in these logs suggests the water table aquifer

beneath the Site is located above the Arundel Clay, in the Patapsco Aquifer, with the first occurrence of

groundwater measured at 8 to 21 ft bgs. The general topography, the occurrence of shallow water table

and flow patterns from adjacent sites suggest potential for the groundwater to discharge to the River. Any

discharge to the River would be influenced by the tidal fluctuations near the Site.

2.5 Surface Water Hydrology and Watershed Characteristics

The Anacostia River watershed encompasses an area of approximately 456 square kilometers (km2) (176

square miles, mi2) within the District of Columbia and Maryland, and lies within two physiographic

provinces, the Piedmont Plateau and the Coastal Plain. Watershed maps are provided in Appendix B.

The Anacostia River begins in Bladensburg, MD, at the confluence of its two major tributaries, the

Northwest Branch and the Northeast Branch, and flows a distance of approximately 8.4 miles before it

discharges into the Potomac River in Washington, DC (Sullivan and Brown, 1988). Because of its

location in the Washington metropolitan area, the majority of the watershed is highly urbanized. An

analysis of geographic information system (GIS) layers prepared by the Metropolitan Washington Council

of Governments (MWCOG) indicates that land use in the watershed is approximately 43% residential,

11% industrial/commercial, and 27% forest or wetlands, with 22.5% of the area of the watershed covered

by impervious surfaces.

The Anacostia River is subject to tidal influence. Based on the United States Army Corps of Engineers

(USACE) condition survey conducted in June 2007, water depths in the Study Area range from

approximately 6.0 ft to 10.0 ft below Mean Low Low Water (MLLW) level. The variation in the river’s


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water surface elevation over a tidal cycle is approximately 0.9 meters (m) (3 feet, ft). The width of the river

varies from approximately 60 m (197 ft) in some upstream reaches to approximately 500 m (1640 ft) near

the confluence with the Potomac, and average depths across a transect vary from about 1.6 m (5.2 ft)

near Bladensburg to about 6.2 m (20.3 ft) just downstream of the South Capitol Street Bridge. During

base flow conditions, measured flow velocities during the tidal cycle have been in the range of 0 to 0.3

meters per second (m/sec) (0 to 1 feet per second, ft/sec) (Katz et al., 2001).

Sedimentation has been a problem in the tidal Anacostia River since colonial times (Scatena, 1987).

Estimated average annual sediment discharge into the tidal embayment of the river was 134,420 tons for

1963 and 137,600 tons for 1981. Because of the low flow velocities in the tidal portion of the river, the

majority of sediment entering the tidal embayment is thought to settle and remain in the tidal river, rather

than being discharged to the Potomac. Based on a variety of methods, including analyses of historical

bathymetry records, dredging records, and pollen profiles of sediment bed core samples, Scatena (1987)

estimated sedimentation rates in the range of 1.2 to 9.1 centimeters per year (cm/yr) (0.5 to 3.6 inches

per year, in/yr). More recently, radiometric dating using Cesium-137 on cores collected near the

Washington Navy Yard (WNY) and the Southeast Federal Center (SEFC) sites indicated a sedimentation

rate of approximately 4.0 to 6.5 cm/yr or 1.6 to 2.6 in/yr (Velinsky et al, 2011). As the sedimentation rates

were measured two to three miles downstream of the Benning Road site, the lower end of the

sedimentation rates are more appropriate for the Study Area.

Based on a review of NOAA’s Office of Coast Survey Navigation Chart #12289 dated October 2010, the

Anacostia channel ends before the Pennsylvania Avenue bridge, which is approximately 1.6 miles

downstream of the Site. According to information provided by the USACE, the most recent navigational

dredging was performed prior to 2002, and included dredging up to Bolling Air Force Base. USACE was

not aware of any dredging ever occurring north of the CSX railroad bridge (1.3 miles downstream of the

Site) other than the cooling water intake dredging conducted by Pepco in 1996.

2.6 Historical Removal Actions and Investigations

A summary of historical environmental investigations and response actions conducted on the Site by

Pepco and the USEPA is presented in Table 1. The locations of these activities are shown on Figure 5.

These activities include five investigation and cleanup efforts in response to PCB material releases,

multiple petroleum underground storage tank (UST) removals and closures, due diligence studies (Phase

I Environmental Site Assessments or ESAs) and various other soil removals conducted by Pepco since

1985. All of these activities and studies occurred on the Landside portion of the Study Area. In addition,

Pepco also conducted three geotechnical studies (CTI, 2009; Geomatrix, 1988; and Hillis-Carnes, 2009)


12

in different areas of the Site as part of its electric system infrastructure improvement projects. These

geotechnical studies provide useful information on Site geology and hydrogeology.

In 1996, Pepco performed dredging at the power plant cooling water intake located north of the Benning

Road Bridge in the Anacostia River. The dredged spoils were used to construct a wetland in the vicinity

of the existing water intake. Dredging and wetland construction activities extended from the Benning

Road Bridge for approximately 900 feet north (Pepco, 1996; Pepco, 1997). .

USEPA conducted a multi-media inspection at the Site in 1997 in connection with the renewal of Pepco’s

NPDES permit (USEPA, 1997). The inspection also included compliance determinations under the

Resource Conservation and Recovery Act (RCRA) and the Toxic Substances Control Act (TSCA). (The

results of this 1997 multi-media inspection are referred to herein as “USEPA, 1997.”) No compliance

issues were noted under RCRA. One spill involving PCB oil was noted inside Building #57; however, the

release was fully contained in a secondary containment vault and no release into the environment

occurred. The cause of the spill was corrected through implementing appropriate management/operating

procedures. USEPA also collected two liquid samples and six residue samples from the storm drain

system. A liquid sample collected at Outfall 013 failed the acute toxicity test due to presence of chlorine

from a leaking relief valve that was discharging chlorine-treated city drinking water. The residue samples

collected from the storm drain system indicated PCB and metal concentrations that exceeded USEPA

Sediment Quality Guidelines (SQGs).

As previously noted, Tetra Tech EM, Inc. conducted an SI at Pepco’s Benning Road Site for the USEPA

under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) program

in 2008 and issued a report in 2009 (USEPA, 2009). Thirteen soil samples were collected from the

former sludge dewatering area (located south of the power plant cooling towers) and 16 sediment

samples and five surface water samples were collected from the Anacostia River. Several metals,

polycyclic aromatic hydrocarbons (PAHs) and PCBs were detected at elevated concentrations in the

former sludge dewatering area and the Anacostia River sediments. With the exception of copper, no

other compounds were detected in the surface water samples. The USEPA 2009 SI Report concluded

that the current management and handling of waste streams, including PCB-containing equipment and

material is well organized and supervised, but linked PCBs and inorganic constituents detected in the

Anacostia River sediments to possible historical discharges from the Site.

2.6.1 Regional Assessment of Anacostia River and Suspected Area-Wide Sources of Impact

This section provides an overview of sediment quality data from the Anacostia River from a regional

perspective and considers data available from the general vicinity of the Benning Road Site. The purpose


13

of this overview is to provide background relative to the current understanding of sediment quality in the

Anacostia River basin and suspected off-Site sources to help formulate the work to be performed as part

of this RI/FS.

For decades, there has been a broad recognition that the water quality and sediment quality in the

Anacostia River is degraded due to a variety of factors, including shoreline habitat degradation, point

sources, non-point sources, combined sewer overflows, input from tributaries, atmospheric deposition,

storm water runoff, and refuse disposal practices (Anacostia Watershed Toxics Alliance [AWTA],

undated). The problems in the river are exacerbated by the tidal nature of the lower Anacostia River;

much of the flow in this portion of the river is tidal, freshwater flows into the tidal waters are relatively

small (Velinsky et al., 2011), and the slow-moving water tends to allow contaminants that might otherwise

be flushed from the system to settle into the sediment column.

A significant number of sediment quality studies have been completed within the Anacostia River, many

of these focusing on known or suspected sources of contamination in the river. Fritz and Weiss (2009)

summarized six possible sources of sediment contamination in the river, while acknowledging that

additional contaminants may exist in sediment or on land abutting the river:

Source Ownership/Comments Contaminants linked to

sediments

Washington Navy Yard (WNY) Department of Defense (DOD),

National Priority List (NPL) site.

PCBs and others

Southeast Federal Center (SEFC) Partly GSA/partly private developer. PAHs, metals, PCBs, and

others

Poplar Point NPS PCBs, PAHs

Washington Gas Light (WGL) WGL and NPS PAHs, metals

Kenilworth Landfill (former DC

dump)

NPS Fill materials had PCBs,

PAHs, metals

Pepco Benning Road Pepco PCBs and PAHs

Source: Fritz and Weiss, 2009


14

Studies on each of these specific sites, as well as broader literature relative to Anacostia River ecology,

were reviewed to assist in understanding prevailing background sediment and water quality conditions and

to provide context for development of the work to be performed as part of this RI/FS. Available reports and

sampling data reviewed included:

Sediment concentrations and toxicity information from 35 databases that were compiled by the

National Oceanic and Atmospheric Administration (NOAA)

(http://mapping.orr.noaa.gov/website/portal/AnacostiaRiver);

A 2001 report from the Academy of Natural Science (ANS) entitled “Sediment Transport: Additional

Chemical Analysis Study Phase II”;

An undated document from the AWTA, entitled “A Toxic Chemical Management Strategy for the

Anacostia River”;

A peer-reviewed paper by Velinsky et al. (2011) entitled “Historical Contamination of the Anacostia

River, Washington, DC;

A 2009 document from the AWTA entitled “White Paper on PCB and PAH Contaminated Sediment

in the Anacostia River”; and

The USEPA 2009 SI Report for the Pepco Benning Road Site, Washington DC.

Results from the Environmental Security Technology Certification Program (ESTCP),

Demonstration Program—The Determination of Sediment PAH Bioavailability using Direct Pore

Water Analysis by Solid Phase Micro-extraction (http://www.serdp-estcp.org/Program-

Areas/Environmental-Restoration/Risk-Assessment/ER-200709/ER-200709)

The findings of these studies consistently showed the presence of PCBs, PAHs, organochlorine pesticides,

metals and to a lesser degree volatile organic compounds (VOCs) in sediment samples collected from up

and down the entire Anacostia River (Velinsky et al, 2011). Velinsky et al. (2011) reported that the surficial

sediment concentrations of many contaminants in Anacostia River sediments have decreased during the

past few decades due to a combination of factors, including improved environmental practices, restrictions

on the manufacture and use of PCBs, and the encapsulation of historic impacted sediment by the more

recent deposit of cleaner sediment. For instance, based on the results of six cores collected from the lower

Anacostia River, total PCB concentrations in surficial sediment fell from as much as 3000 micrograms per

kilogram (µg/kg) in the late 1950’s to 100-200 µg/kg in 2011.

http://mapping.orr.noaa.gov/website/portal/AnacostiaRiver/


15

The USEPA 2009 SI Report is the most comprehensive for surficial sediments in the vicinity of the Site.

According to this report:

Analytical results obtained during the SI sampling event indicate that the contaminants of potential

concern associated with Anacostia River sediments are PAHs, PCBs and inorganic compounds

(metals);

PAHs are essentially ubiquitous in sediments of Anacostia River in the vicinity of the Site

(Appendix C). The report also notes potential PAH sources located upstream of the Site, including

numerous combined sewer outfalls;

PCBs, specifically, aroclor-1254 and aroclor-1260 were detected in sediment samples above the

screening concentrations established by the USEPA Biological Technical Assistance Group (BTAG)

and NOAA for aquatic life. Several metals were also reported above these screening

concentrations;

No VOCs, semi-volatile organic compounds (SVOCs), pesticides or PCBs were reported above

detection limits in the surface water samples collected during the SI. Of the inorganic constituents,

only copper was detected at a concentration slightly above the corresponding USEPA Region III

fresh water quality criterion; and

USEPA concluded that historical releases from the Site contributed to the contamination

documented in the Anacostia River sediments in the vicinity of the site based on residue samples

USEPA collected from the Benning storm water system during USEPA’s 1997 multi-media

inspection.

The AWTA (2000) report regarding the Anacostia River indicates that concentrations of PAHs and PCBs in

sediments exceeded conservative screening-level ecological benchmarks throughout the entire river with

areas of relatively greater contamination primarily oriented to depositional areas of the lower half of the river

(below Kingman Lake), plus some additional, isolated locales of the river where sediment is being

deposited. The AWTA (2000) report identified the following six areas of interest recommended for further

investigation including the vicinity of the Benning Road Site:

Area 1: Near O Street/SEFC/WNY (PCBs, PAHs, and metals);

Area 2: Upstream from CSX lift bridge (PCBs and PAHs);


16

Area 3: Between the 11th Street and CSX bridges (PAHs);

Area 4: Off Poplar Point (PAHs and some PCBs);

Area 5: Upstream from the Pepco Benning Road facility (PCBs); and

Area 6: the area in between the “hot-spots” identified in Areas 1-5 above, and within the

depositional zone of the lower river extending roughly between the South Capitol and 12th Street

Bridges.

The AWTA (2000) report identified approximately 60 acres of PAH or PCB contaminated “hot spots”

recommended for capping (hot spots were identified as areas with concentrations exceeding the mean plus

two standard deviations; 879 µg/kg for PCBs and 35,440 µg/kg for PAHs). One relatively small hot spot was

identified in the vicinity of the Site.

A review of NOAA’s 35 databases (accessed through NOAA Query Manager Program) indicates that

several hundred Anacostia River surficial sediment samples have been collected from the mouth of the

Anacostia River to points upstream of the Benning Road Site. Relative concentrations of total PCBs and

total PAHs in surficial sediment samples within four miles of the Site are illustrated on GIS plots provided

in Figures 1 and 2 of Appendix C. The tabular summary below presents summary statistics for these

compounds in Anacostia River sediment:

Study Area PCBs PAHs

Number of

Samples

Concentration (µg/kg) Number of

Samples

Concentration (µg/kg)

Minimum Mean Maximum Minimum Mean Maximum

Benning

Road Study

Area (a)

16 40 Not

available

2,510 16 2,020 Not

available

14,920

Anacostia

White

Paper (ANS

2000 data

only) (b)

124 2 181 1,643 125 495 11,742 56,330

Anacostia

White

Paper (All

studies) (b)

295 Not

detected

579 12,000 314 100 16,619 211,300


17

(a) Source: USEPA, 2009. Sum of aroclors and total PAHs

(b) Source: Anacostia Sediment Capping White Paper, undated. This paper evaluates total PCBs

and total PAHs from (1) an Academy of Natural Sciences (ANS) Study (ANS, 2000), which was

“relatively comprehensive”, and (2) from 12 specific studies (plus the ANS study) conducted

between 1990 and 2003 on the river using a variety of sampling methods and protocols.

A review of these data suggests that USEPA 2009 SI data, while clearly containing PCBs and PAHs,

must be reviewed within the overall construct of the urbanized Anacostia River corridor. USEPA in their

1997 Multi-media Inspection Report notes that PCB concentrations in storm sewer residue at the Site

were above the SQG, but less than concentrations found in similar samples collected at WNY and SEFC.

With regard to PAHs, the USEPA (2009) SI report indicates that contaminated sediments are located

upstream and downstream of the Site, and that “PAHs are essentially ubiquitous in sediments of the

Anacostia River in the vicinity of the site” and that “…sources of PAHs are located upstream of the

Benning Road facility. These potential sources included numerous combined sewer storm water outfalls

located upstream of the site.”

Although many stakeholders are engaged in concerted efforts to prevent contaminant loading into the

Anacostia River, one of the more substantial challenges is related to the combined sewer overflow (CSO)

systems that serve approximately one third of the District of Columbia (AWTA, undated;

http://www.dcwasa.com/wastewater_collection/css/default.cfm). The District’s CSOs are antiquated

systems (many of which date from the 1880’s) that allow urban runoff and raw sewage to bypass

treatment systems during rain events. During dry periods, sanitary wastes collected in the CSO system

are treated at the Blue Plains Advanced Wastewater Treatment Plant; however, during periods of

significant rainfall, the capacity of the CSO system is exceeded, and a mixture of storm water and sanitary

wastes is directly discharged into the District’s water bodies, including the Anacostia River. There are

currently 53 permitted CSO outfalls in the District operated by DCWASA.

According to AWTA (undated), an average of 82 releases of combined stormwater and sanitary wastes

occur per year due to this outdated system. At the time of AWTA report publication, these releases were

reported to allow a discharge volume of approximately 2.14 billion gallons of contaminated waste-water

from 11 major CSOs to enter the river system on an annual basis. DCWASA recently developed a model

that predicted that in excess of 93% of CSO flow volume was contributed by two CSO systems, at Main

and O Street (CSO 010, the O Street Pumping Station) approximately 3.4 miles downstream from the

Site, and at the Northeast Boundary (CSO 019), approximately 1.2 miles downstream from the Site. A

map showing the CSO Outfalls and drainage areas is provided in Appendix B.

http://www.dcwasa.com/wastewater_collection/css/default.cfm


18

More recent data from the DCWSA website highlights the CSO concern on the Anacostia River

(http://www.dcwater.com/wastewater_collection/css/CSO%20Predictions.pdf). During the first 3 months of

calendar year 2012, approximately 44.7 million gallons (MG) of CSO overflow were released into the river.

Approximately 66% (29.48 MG) were attributable to CSO 19 (the Northeast Boundary CSO), whereas an

additional 18.6% (8.33 MG) were attributable to CSO 10 (the O Street Pumping Station).

Potential sources of contamination to the river in the immediate vicinity of the Site include the Kenilworth

Landfill and the Langston Golf Course. The following paragraphs describe these studies.

Kenilworth Park Landfill is one of several properties along the Anacostia River that are suspected sources

of contamination. Kenilworth Park landfill is separated into two areas: the Kenilworth Park North (KPN)

landfill and Kenilworth Park South (KPS) landfill separated by Watts Branch, a tributary to the Anacostia

River (Figure 4), with the southern portion of the KPS being immediately adjacent to the Study Area.

KPS and KPN are part of the 700-acre, Kenilworth Park and Aquatic Gardens, which is part of the

National Park System. KPN operated from 1942 to 1968 and in 1968 the operations moved to KPS. By

the 1970s, the entire landfill was closed and capped (with a vegetative cap), and the land was converted

for use as a park (NPS, 2008). Wastes deposited in the landfills included municipal waste, incinerator

ash, and sewage sludge. During its operation between 1950s and 70s, the landfill extended into the

Anacostia River and no barriers were constructed to prevent migration of wastes mixed with soil into the

water (AWTA, 2009). Ecology and Environment, Inc. completed remedial investigations (RIs) at KPN and

KPS separately in 2007 and 2008, respectively for NPS (NPS, 2007; NPS, 2008). COPCs identified by

the two RIs included: PCBs, PAHs, dieldrin, arsenic, lead and methane. The KPN RI concluded that

groundwater probably is impacting some sediments adjacent to the Site (NPS, 2007). Feasibility Studies

have been recommended for both landfills.

Ecology & Environment, Inc. also performed a Preliminary Assessment/Site Inspection (PA/SI) of

Langston Golf Course for NPS in 2001. Langston Golf Course is located along the west bank of the River

across from the Site. It is one of a number of sites along the Anacostia River that were used by the

District as open burning/open dumps for municipal waste disposal from approximately 1910 to 1970

(NPS, 2001). An open dump with open burning existed on the west bank of the River until the early

1950s. The former District landfill was placed directly into the Kingman Lake without any barrier, and

landfill wastes mixed with soil extended into the water. The PA/SI identified the presence of chemicals

(PAHs, antimony, arsenic, iron, and lead) exceeding action levels in the fill material under the site. Lead

showed elevated levels and was identified as the greatest concern among the identified chemicals. The

PA/SI concluded that there are no current exposure pathways by which the landfill wastes buried under

the golf course can affect public. The study also concluded that groundwater impacts on adjoining

http://www.dcwater.com/wastewater_collection/css/CSO%20Predictions.pdf


19

surface water are extremely slight. The study recommended that the site be maintained in its current use

as a golf course and be reevaluated if site use changes.

AECOM incorporated the findings from various studies discussed above, and response actions conducted

by Pepco (discussed under Section 2.6) into the CSM and Work Plan development. The CSM

development is discussed in Section 3.0.


20

3 Conceptual Site Model

Information obtained from reviewing the data described in Section 2 regarding contaminant sources,

pathways, and receptors has been used to develop a preliminary CSM of the Study Area to evaluate

potential risks to human health and the environment. The CSM identifies sources of contamination,

affected media, routes of migration, human and environmental receptors, and potential routes of

exposure after accounting for existing institutional, administrative and engineering controls at the Site

(e.g., 24-hour controlled Site access, paved surfaces and employee hazard communication training

program) that may eliminate or control exposures to on-site and off-site receptors. The CSM is useful in

identifying data gaps and further sampling needs, and potential remedial technologies to mitigate any

identified risks. It is also important for understanding the effects of both anthropogenic and natural factors

on chemical concentration patterns. This preliminary CSM is a “living document”, and will be refined in an

iterative manner as new information becomes available as the RI/FS process progresses. A pictorial

representation of the preliminary CSM is presented as Figure 9 and described further in the following

paragraphs.

3.1 Landside

Current understanding of potential sources and impacted media on Landside of the Study Area are

discussed in Section 2, and summarized in Tables 1 and 2, and shown on Figure 5. A brief summary of

this information as it pertains to the CSM development is provided below.

Six petroleum USTs were either removed or closed in place in accordance with the regulations in

force at the time of their closure. A potential exists for residual petroleum hydrocarbons at these

UST sites.

PCB cleanups were conducted at the Site as noted in Table 1. Residual concentrations of PCBs in

subsurface soils in these areas may range from 1-25 parts per million (ppm).

Elevated concentrations of PAHs, PCBs and heavy metals (lead, copper, nickel, vanadium and

zinc) have been detected in the former sludge dewatering area immediately south of the cooling

towers. Certain PAHs and PCBs exceeded the USEPA soil screening levels. This area measures

approximately 14,400 square feet. No removal actions have been performed in this area; however,


21

this area was graded and covered with gravel to prevent erosion and migration of impacted

material.

Several areas on the site (as noted in Table 2 and discussed in Section 4.2.1 below) have the

potential to contain petroleum hydrocarbons, PAHs, PCBs, and heavy metals given the 100-year

industrial history of the site. The site history includes former coal use and current #4 fuel oil use.

There is a significant amount of site-specific subsurface geological information available from

Pepco’s previous geotechnical activities and activities on adjacent sites. The data indicates the site

is underlain by the Patapsco Formation potentially containing two water bearing zones separated by

a clay unit. The Patapsco Formation is underlain by Arundel Clay regional confining unit at depths

ranging from 42 to 73 feet beneath the Site. Because the borings and observations were made by

different consultants over a long period of time, this information should be confirmed with a limited

set of new borings.

There is limited chemical data for subsurface soil in many areas of the Site, and there are no

existing groundwater monitoring wells, so current groundwater conditions are not known. In

addition, the potential impacts from the KPS landfill site on Site groundwater are not well

understood.

Currently, little is known about the volumetric flux of ground water to the Anacostia River in the area

of the Site. Based on the limited information available, it is possible that the shallow groundwater

zones beneath the Site could discharge to the Anacostia River during the low tide conditions. As

part of this RI/FS Work Plan, monitoring well installation and aquifer testing are proposed to

characterize the potential for groundwater discharge. The hydraulic data will be used, along with

precipitation and aquifer recharge calculations, to develop a water budget including an estimate

groundwater flux from the Site.

At the Site, the Patapsco Formation and Arundel Clay has also been identified at relatively shallow

depths. Rainfall recharge to the water table is limited by impermeable surface cover, which covers

the majority of the Site. The low rates of recharge to the water table would, therefore, limit

discharge of groundwater to surface water from the Site. The hydraulic data collected in the RI/FS

will document inflows to (e.g., precipitation) and outflows (e.g., storm water runoff, groundwater

recharge, etc.) from the Site.

The 2008 SI report indicated that historical releases via storm drains may have contributed partially

to the impacts noted in the Anacostia sediments. This potential pathway will be investigated further

during the RI/FS.


22

The nature and extent of potential constituents of potential concern (COPC)-impacted sediment are

only partially characterized or delineated along most of the Site.

Direct and indirect human health exposure pathways on the Landside portion of the Site have been

found to be incomplete or insignificant because:

1. Access to the Landside portions of the Study Area is limited by perimeter fencing and 24-hours

per day, 7 days per week security;

2. The presence of impervious surfaces/gravel cover prevents contact with surface soil;

3. Contact with subsurface soil is restricted by health and safety procedures and an employee

hazard communication program to prevent or manage worker’s exposure during excavation

activities; and

4. Groundwater is not used as a local source of drinking water.

These elements will be evaluated as institutional controls during the finalization of a remedial action plan, if

warranted by the findings of the investigation.

3.2 Waterside

The Waterside CSM explores the potential past and present mechanisms of constituent movement from

the Site into the Anacostia River as well as the distribution of various sediment environments/habitats in

the river as they might affect constituent distribution. The CSM summary presented in this section

describes the origin (sources) of COPCs, as well as potential transport pathways, exposure pathways,

and receptors. The CSM will be updated as more data becomes available through the implementation of

RI/FS activities. Several sources of COPCs in sediment in the vicinity of the Site may exist, including:

Historic discharges through Outfall 013 and overland flow from the Landside portion of the facility;

Groundwater which may discharge to the surface water of the River;

Storm sewers from other facilities, combined sewer outfalls, and sites such as the Kenilworth

Landfill and Langston Golf Course former landfill; and

Industrial activities in the upper anthropogenically-impacted Anacostia River and its main

branches and tributaries.

Additional CSM elements include the following:


23

COPCs in sediments associated with the Site may include PCBs, PAHs, and metals resulting

from operation and maintenance of the power plant and equipment associated with Pepco’s

electrical transmission and distribution system, as well as chemicals which may have been

released from other site- or non-site-related activities;

Sedimentation rates in the river may have resulted in sediment deposition of COPCs on top of

sediments adjacent to the Site from sources not related to the discharges from the Site;

Likewise, sedimentation of the river has the potential to encapsulate historical discharges from

the Site into sub-surficial horizons beneath the bio-active zone (the bio-active zone is the upper 4

to 6 inches of sediment that contains the benthic organisms);

On-going sources associated with storm water discharge are controlled at this Site;

Potential transport pathways for COPCs from the Benning Road facility to adjacent sediments are

sheet flow from the Site to the water column and sediments, as well as historic storm water

discharges to the water column and sediments.

The tidal influence of the river is unknown with regards to COPC distribution adjacent to the Site;

and

Human health exposure pathways are most likely associated with consumption of contaminated

fish, although the Anacostia River and Potomac River are currently under a fish consumption

advisory imposed by the DDOE. This advisory provides the following advice to the public relative

to consumption of fish from DC waters and indicates that the advisory is due to the presence of

PCBs and other chemical contaminants:

Do Not Eat: channel catfish (Ictalarus punctatus), carp (Cyprinus carpio), or American eel

(Anguilla rostrata)

May Eat: One-half pound per month of largemouth bass (Micropterus salmoides) or one half-

pound per week of sunfish or other fish

Choose to Eat: Younger and smaller fish of legal size

The practice of catch and release is encouraged.

In addition, the DDOE advisory provides limited guidance regarding skinning of fish, trimming fat,

and cooking of fish.

Ecological exposure pathways are most likely associated with benthic macroinvertebrates, fish,

and piscivorous birds and mammals.


24

4 Work Plan Rationale

This section describes the data quality objectives (DQOs) development process and presents an overall

approach for completing the RI/FS.

4.1 Data Quality Objectives

The DQOs for the Landside and Waterside areas were developed using the USEPA’s DQO process, a

multi-step, iterative process that ensures that the type, quantity, and quality of environmental data used in

the decision making process are appropriate for its intended application. The Landside and Waterside DQO

development process is presented in Tables 3 and 4, respectively.

The DQOs for this investigation are:

To characterize environmental conditions within the Study Area and refine the CSM

To collect additional data to update existing Landside and Waterside datasets from previous

investigations so that nature and extent of impacts can be defined

To collect data to determine whether and to what extent past or current conditions at the Site

have caused or contributed to contamination of the Anacostia River

To collect data within the Anacostia River to identify potential Site-related, near-Site and far-Site

sources of COPCs in sediment and surface water

To collect hydraulic data to better understand the site-specific hydrogeology and evaluate the

volumetric flux of groundwater to the Anacostia River

To collect data to better understand the Site storm drain system and associated discharge to the

Anacostia River at various outfalls

To collect data to support performance of Human Health and Ecological Risk Assessments

To collect data to support a Natural Resources Damage Assessment (NRDA) evaluation

To collect data to support development and evaluation of remedial alternatives

There are several analytical levels of data quality available to achieve the DQOs. These levels are

typically designated as follows:

Level I – Field screening or analysis using portable instruments, calibrated to non-compound

specific standards;


25

Level II – Field analysis using portable instruments, calibrated to specific compounds;

Level III – USEPA recommended performance based methodologies such as those outlined in

USEPA SW-846;

Level IV – USEPA Contract Laboratory Program (CLP) Routine Analytical Services (RAS)

methods; and

Level V – Other internationally-recognized and/or non-standard analytical methods.

Field-screening data will be used in the Landside investigation to interpret lithologic units and aid in the

identification of the presence or absence of a release in an area. In addition, field screening data will be

used in the Waterside investigation to understand the depth of the water column, configuration of the river

bottom and identification of utilities in the proposed investigation area.

Field screening data will be used as part of a weight-of-evidence approach in conjunction with laboratory

data and geologic information to delineate impacts in the context of the CSM. Additionally, field screening

and observations will be used by the field team to evaluate and adjust sampling depths and locations as

needed. This approach to the field investigation is a key component of this dynamic work plan.

Landside and Waterside field screening activities will be conducted under Level I data quality protocol.

Both Landside and Waterside field measurements [i.e., pH, temperature, turbidity, photoionization

detector (PID), x-ray fluorescence (XRF)] will be completed under Level II data quality protocol. Samples

submitted for fixed laboratory analysis and accredited on-site mobile laboratory will be analyzed, at a

minimum, under Level III data quality protocol. Level IV or V could be used for specialty methods such as

high resolution PCB analysis or forensic analysis.

4.2 Work Plan Approach

In order to meet the RI/FS project schedule expeditiously, the planned investigation will incorporate an

iterative, dynamic approach to the investigation using field screening techniques, field-based decision-

making and real-time evaluation of data while crews are still in the field, as necessary. In consultation with

DDOE and the Pepco Project Manager, the AECOM Field Team Leader will be given authority to adjust

sampling locations, as appropriate based on field conditions. The sampling program will incorporate an

adaptive management approach that allows the use of screening parameters to screen larger areas to help

focus resources on potential problem areas.Field and laboratory data will be rapidly uploaded to the project

database to allow a timely evaluation of results, and thereby allowing near real-time adjustments to the field

investigation, as necessary, to complete the delineation of impacts encountered. Pepco will use an

accredited mobile laboratory to facilitate rapid characterization.


26

4.2.1 Landside Investigation

The Landside investigation program will include three phases of work, each phase providing necessary

information for the planning of the successive phase of work. Landside data collection program is

summarized in Table 5. Phase I activities will involve sampling of surface soils and storm drains. In

addition, Phase I will first involve the screening of the Site using electrical resistivity imaging (ERI) to

identify potential anomalies,followed by soil borings to calibrate the electrical signals with lithologic and

chemical sampling.

ERI also provides useful information on soil and groundwater zones impacted by light non-aqueous

phase liquids (LNAPLs) and/or dense non-aqueous phase liquids (DNAPLs). These zones will be

targeted during Phase II using the direct push technology (DPT) (Geoprobe®) borings to delineate

potential zones of impact and identify any continuing sources of contamination. Additional direct push

borings will be conducted during Phase II to collect soil and groundwater samples and characterize

horizontal and vertical extent of any impacts found using PID and XRF field instruments, and total

petroleum hydrocarbon (TPH) and PCB aroclor analysis using an on-site mobile lab.

Phase III will involve a detailed hydrogeologic investigation involving the installation of monitoring wells,

water level gauging, aquifer testing and groundwater monitoring. The locations of the monitoring wells

will be based on results from ERI and DPT data collected in Phases I and II.

To help guide all of these Landside investigation activities, AECOM identified several “Target Areas” on

the Site based on historical investigations and remediation, UST closures, former and current operations

that could have a potential for Site impacts. These Target Areas are presented in Table 2 and depicted

on Figure 5. It should be noted that Pepco completed investigations and/or cleanups in Target Areas

with PCB and petroleum releases in accordance with the District regulations. Some target areas have

been identified based on PCB handling operations, which are in compliance with applicable regulations,

and current fuel storage. Therefore, the purpose for these Target Areas is to serve as a guide to steer the

RI field activities. Target Areas may be grouped together during the initial phases of investigations. As

investigation activities proceed in an iterative fashion, they will focus on any impacts observed in or

around the Target Areas.

4.2.2 Waterside Investigation

The Waterside investigation will focus on defining the nature and extent of COPCs in sediments adjacent

to the Site and at selected background locations. There is a high degree of uncertainty associated with

sediment COPCs originating from the Site, due to potential contributions from other sources, the nature of


27

the tidal river system, and sediment deposition. After a review of Site-related documents, the following

potential data gaps were identified:

The horizontal and vertical extent of COPC-impacted sediment proximate to the Site requires

further delineation;

The potential contribution of groundwater that discharges from the Site to the river is not well

understood;

The source(s) of any COPCs in sediments proximate to the Site have not been adequately

determined. Given the high potential for other sources of these compounds, it is unlikely that all

COPCs identified within the sediment would be attributable solely to the operations at the Site.

Developing an understanding of Site-related impacts to surface water and sediment in this urban

river system requires information such as PAH and PCB fingerprinting/pattern matching (referred

to as forensic analysis).

The effects associated with potential exposure to Site-related sediment COPCs on Anacostia

River human and ecological receptors have not been adequately assessed and the potential role

of non-COPC stressors such as grain size, CSOs, seasonal fluctuation in dissolved oxygen (DO)

is not adequately understood. It is possible that these non-chemical stressors also play a role in

posing a potential risk to ecological health in the vicinity of the Site.

This Work Plan has been designed to address these data gaps, as well as other topics, through the

collection of additional data and further review of existing information.

Data for the Waterside area will be collected in two phases. Phase I will involve bathymetric and utility

surveys at on-site and background locations. Surface water and sediment sampling will be conducted

under Phase II. Sediment samples will be collected using barge-mounted Vibracore™ equipment. An on-

site mobile lab will be used to characterize the extent of sediment impacts using PCBs aroclor analysis.


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5 RI/FS Tasks

This section provides a brief discussion of the various RI/FS tasks. Detailed sampling procedures,

operating procedures, calibration and analytical procedures will be discussed under the SAP.

5.1 Project Planning

The project planning task involves preparing necessary project plans (Work Plan, SAP and HASP),

obtaining all required permits, clearances, and site access. In addition to obtaining utility clearances as

needed, the following permits requirements have been identified:

Approval of the Work Plan, SAP and HASP by DDOE.

Drilling permits for the landside and waterside sampling activities from the District Department of

Consumer and Regulatory Affairs (DCRA).

Permit from USACE, Baltimore District, for working in the Anacostia River. It is expected that the

sampling would be covered under the Nationwide Permit (NWP) #5 or #6. An individual Water

Quality Certification must be obtained from DDOE to authorize the use of these NWPs.

A permit would be required from the NPS to access the River and conduct sampling in the River.

5.2 Field Investigation Activities

The field investigation activities are designed to characterize conditions in soil, groundwater, surface

water and sediment; further refine the CSM; and collect data to support risk assessment and NRDA.

Data gaps identified during the review of existing data were used to guide the scope of this investigation.

Field investigation activities are divided into Landside and Waterside activities and are described below.

All field investigation activities will be conducted in accordance with the approved SAP and HASP.

5.2.1 Landside Investigation

Phase I, Task 1: Utility Clearance

Various forms of underground/overhead utility lines or pipes may be encountered during site activities.

Utility plans will be obtained and reviewed while selecting sampling locations. Prior to the start of intrusive

operations, utility clearance will be conducted by public and private utility locators in proposed investigation

areas. Miss Utility will be contacted for the identification of all recorded public utilities servicing the Site.

Following public utility identification, a private utility locating contractor will be utilized to identify and locate


29

any utilities that Pepco is unable to clear. A review of available as-built drawings will be conducted to locate

any additional subsurface structures prior to intrusive activities. If insufficient data is available to accurately

determine the location of the utility lines within the proposed investigation area, AECOM will hand clear or

use soft dig techniques to a depth of at least five ft bgs in the proposed areas of subsurface investigation.

Phase I, Task 2: Surface Soil Sampling

The purpose of surface soil sampling is to evaluate surface soil quality and to help plan the DPT

investigation. The analytical data will also be used to develop correlations with field instruments to be

used for screening during Phase II activities. Surface soil samples will be collected from within the top 12

inches of the subsurface after coring through existing pavement or ground cover. Each sample will be

screened with a field PID and XRF instrument and the results will be recorded. As shown in Table 5, a

total of 25 surface samples will be collected from various portions of the Site. The surface soil samples

locations will be distributed to get a good coverage of the entire facility, while using some biased samples

to address the Target Areas presented (Figure 10).

Phase I, Task 3: Storm Drain Sampling

AECOM will identify the storm drains in locations that would be impacted by potential releases, based on

evaluation of data from prior sampling events, site inspections, and discussions with Pepco personnel.

The purpose of storm drain sampling is to determine, if current or historical discharges from the storm

drain system contributed to contamination in the River. A total of five sediment/residue and five water

samples will be collected from Site storm drains. Up to two of these locations will be selected for forensic

analysis.

Phase I, Task 4: Electrical Resistivity Imaging (ERI)

ERI techniques are commonly used in environmental site characterization and involve the measurement

of electrical conductivity/resistivity of the ground. A variation of the ERI technology known as GeoTrax™

is offered by Aestus, LLC. Each GeoTrax Survey™ will be performed by installing specialized 3/8-inch

diameter stainless steel electrodes into the ground along a straight line or transect that could run

hundreds of feet long depending on the target depth of investigation. The electrodes are hammered into

the ground just far enough to get electrical contact with the earth, typically 6 to 15 inches. The resulting

data is processed using proprietary algorithms to produce a color-coded, high-resolution, 2-dimensional

or 3-dimensional image that can be used to identify anomalies that represent changes in subsurface

lithology, buried objects, and LNAPL/DNAPL plumes, and chlorinated compounds such as PCBs.

GeoTrax™ imaging can be used as a screening tool and when calibrated with actual lithologic and


30

chemical data collected from a direct push boring, it provides a rapid site characterization tool. Up to

eight GeoTrax™ transects will be run along cross section A-A’, in the former sludge dewatering area, and

other Target Areas to the top of the Arundel Clay unit as identified in Figure 10. Calibration borings will

be performed using a combination of soil borings in Phase I and direct-push borings under Phase II.

Phase I, Task 5: Soil Borings

A geotechnical investigation will be conducted to aid in the verification of the existing data and design of

monitoring wells. Five soil borings (SB-1 through SB-5) will be installed at the approximate locations

shown on Figure 7. The soil borings will be advanced approximately 10 feet into the confining layer

(Arundel Clay) using a Hollow Stem Auger (HSA) Drill rig to obtain split-spoon and Shelby tube samples.

Split-spoon samples will be obtained using the standard penetration test (SPT) in accordance with the

American Society for Testing and Materials (ASTM) Standard D1586. The blow counts (hammer strikes)

required to advance the sampler a total of 18 inches or 24 inches will be counted and reported. Soils will

be logged in accordance with the Unified Soil Classification System (USCS). Split spoon samples will be

collected continuously from the surface to the water table and then every five feet from the water table to

the terminal depth of the boring. Soil samples will be field screened for VOCs using a calibrated PID. Up

to five Shelby tube or disturbed samples (from drill cuttings) will be collected from each boring in

accordance with ASTM Standard D1587 and analyzed for ASTM Permeability, Grain size and Atterberg

limits. To aid in the identification of the Arundel Clay, three Shelby tube samples will be collected from

the bottom (approximately 10 feet into the confining unit) from three selected soil borings and analyzed for

ASTM Permeability, Grain size and Atterberg limits. One split-spoon soil sample from each soil boring will

be collected from the middle of the water table aquifer and analyzed for ASTM Grain size and Atterberg

limits.

Groundwater levels will be collected during installation of the geotechnical borings and 24 hours following

completion of the borings. Dedicated investigative tooling and materials will be properly decontaminated

in accordance with the SAP. Disposable materials and supplies (e.g. tubing, personal protective

equipment (PPE), etc.) will be disposed of with the municipal waste. Soil cuttings generated during boring

installation will be temporarily staged on-site in 55-gallon drums while awaiting characterization.

Upon completion of soil boring activities, soil borings will either be converted to monitoring wells (if

determined feasible) or properly abandoned with grout using a tremie pipe to the maximum extent

possible. The ground surface will be restored to match the existing surface cover. Soil boring locations

will be surveyed (x, y and z-planes) into existing site datum by a licensed surveyor.


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Phase II, Task 1: DPT Subsurface Investigation

Following the completion of Phase I, DPT borings will be advanced in and around Target Areas identified

on Figure 5 as well as any anomalies identified by the ERI activities. As described in Section 2.0, Target

Areas identified on Figure 5 are for guidance purposes only. Several of the Target Areas that are

geographically close may be grouped together and investigated as one area based on field logistics. A

total of 40 DPT soil borings are planned. Soil borings will be advanced to approximately 5 ft below the

first water table or refusal, whichever is encountered first. Soil cores will be screened continuously using

a PID. A field geologist will continuously log the cores in accordance with the USCS to the terminal depth

of the boring.

Soil samples will be collected from three depths and subjected to screening using an XRF field

instrument, and total petroleum hydrocarbon (TPH) and PCB aroclor analysis using an on-site mobile

laboratory. Boring locations and characterization parameters will be adjusted based on the screening

data. Investigation activities will focus on any Target Areas where impacts are observed. Groundwater

samples will be collected in-situ from the within the top five feet of the water table using a discrete

sampling DPT tool. It should be noted that groundwater sample intervals may be adjusted based on the

results of the ERI screening. Groundwater and soil samples will be submitted for laboratory analysis as

noted in Table 5. A subset (approximately 20%) of the samples will be subjected to metals analysis for

confirmation of the field XRF data.

Reusable investigative tools and materials will be properly decontaminated in accordance with the SAP.

Disposable materials and supplies (e.g. direct push liners, tubing, PPE, etc.) will be rinsed and disposed

of as ordinary solid waste. Soil cuttings and purge water generated during boring installation will be

temporarily staged on-site in 55-gallon drums while awaiting characterization.

Upon completion of soil boring activities, soil borings will be properly abandoned with grout following the

DDOE guidance. The ground surface will be restored to match the existing surface cover. Soil boring

locations will be surveyed (x, y and z-planes) into existing site datum by a licensed surveyor.

Phase III, Task 1: Monitoring Well Installation Following the completion of Phase II, monitoring wells will be designed and installed based on the results

of ERI, DPT, and geotechnical investigative activities. The number or location of the wells cannot be

determined at this time. Upon review of results from Phase I and Phase II, Pepco will prepare and submit

a Work Plan addendum to DDOE to describe the selection of monitoring well locations. Upon DDOE

approval of the Addendum, monitoring wells will be installed using a drill rig equipped with 12.25-inch

outer diameter hollow stem augers (8.25-inch inner diameter). Split-spoon samples will be obtained in


32

accordance with the ASTM Standard D1586.Soils will be logged in accordance with the USCS. Split-

spoon samples will be collected continuously from the surface to the water table and then every five feet

from the water table to the terminal depth of the boring. Soil samples collected from the vadose zone will

be field screened using a PID for VOCs.

The monitoring wells will be constructed using two-inch diameter Schedule 40 polyvinyl chloride (PVC)

well casing and slotted PVC well screen. If two water-bearing zones within the Patapsco formation are

confirmed, the wells will be constructed of 2-inch diameter PVC casing as nested wells with two discrete

screened intervals. A certified clean sand filter pack will be installed in the annular space between the

borehole and the well screen and casing from the bottom of the boring to approximately one foot above

the screened interval. Approximately two feet of bentonite clay will then be placed on top of the sand

pack and hydrated to form a seal above the sand. After allowing the bentonite to set, the remaining

portion of the annular space will be tremmie grouted with a bentonite-portland cement mixture to grade.

Each monitoring well will be completed inside a traffic-rated 18-inch road box/well vault. Upon completion

of monitoring well installation, construction logs will be completed providing the details of the well

construction and depth.

Following installation, the wells will be developed using a surge block and submersible pump. The surge

block will beused inside the well to flush fine sediments from the sand filter, grade formational sediments,

and remove the sediment lining on the borehole that is inherent in most drilling methods. After the well is

surged, a submersible pump will be lowered into the well and groundwater will be withdrawn. Temperature,

pH, specific conductance and turbidity readings will be monitored and pumping will proceed until the

readings have stabilized or five well volumes have been removed.

Drill cutting and development water will be managed as described in Section 5.2.3 below. Top of casing

elevations and locations for each groundwater monitoring well will be surveyed into existing Site datum by

a licensed surveyor. In addition, one or more river gauging stations will be established in the Anacostia

River and surveyed as well.

Phase III, Task 2: Monitoring Well Gauging and Sampling

All groundwater monitoring wells will be allowed to equilibrate for a minimum of 7 days after development

prior to groundwater sample collection. Prior to thegroundwater sampling, a site-wide water level

measurement event will be performed during the period of slack tide in order to determine groundwater

elevations at the Site and accurately characterize local groundwater flow conditions. In addition, the

Anacostia River elevations will be determined concurrently by collection of water levels at gauging stations


33

with referenced elevations surveyed to the same control datum as the monitoring wells. The surface water

elevations will also be measured during the period of slack tide to determine the elevation relationship

between the site groundwater and the Anacostia River. Two such gauging events will be conducted.

Groundwater samples will be collected from monitoring wells with portable bladder pumps using disposable

bladders and low-flow sampling techniques. Groundwater samples will be collected and analyzed as noted

in Table 5. Disposable sampling materials, decontamination water and purge water will be containerized

and managed as described in Section 5.2.3 below.

Phase 3, Task 3: Aquifer Testing

Aquifer testing will be conducted using slug testing techniques. Approximately two weeks following pump

test activities, slug testing will be conducted on select monitoring wells to characterize hydraulic properties

of the water table aquifer. The tests will consist of falling-head and rising-head slug tests to determine the

hydraulic conductivity of the material in the vicinity of each well. The tests will proceed until the water levels

have recovered to within 10% of the static pretest levels or 24 hours have elapsed. Slug testing data will be

interpreted using the Bouwer-Rice solution for an unconfined aquifer on Aqtesolv™ or similar aquifer test

analysis software.

5.2.2 Waterside Investigation

The Waterside investigation is designed to evaluate potential sources of constituents in the sediment of the

Anacostia River in the vicinity of the Site, provide horizontal and vertical delineation of constituents in the

sediment, and determine the potential effects associated with exposure to sediment constituents on

Anacostia River receptors (i.e., human and ecological receptors). Based on the results of prior sampling, the

investigation will focus on PAHs, PCBs, and metals, with limited screening samples for VOCs, SVOCs,

pesticides, and dioxins/furans. This information will be used to support the risk assessments and the

NRDA.

This investigation will primarily address sediment conditions within the Waterside Investigation Area, an

area of the Anacostia River approximately 10 to15 acres in size including approximately 1,500 linear feet to

the south (approximately 1,000 feet south of the Benning Road Bridge) and 1,000 linear feet to the north of

the Site’s main storm water outfall area (Figure 10). The proposed study area is based on its proximity to

the Site and results from the USEPA 2009 SI Report.

The Waterside investigation will focus on defining the nature and extent of constituents of potential concern

in sediments adjacent to the Site and at selected background locations. A progressive elimination approach


34

will be incorporated into the Waterside sampling program to allow the use of screening parameters to

screen larger areas and help focus resources on potential problem areas. Following the evaluation of these

findings, additional investigation may be recommended to refine the delineation of chemical data or provide

additional site-specific information from selected portions of the study area.

The Waterside investigation will use a systematic sampling grid to determine sediment and surface water

sampling locations during the Waterside investigation (Figure 11). This grid will consist of 45 sampling

locations on ten (10) sampling transects positioned perpendicular to the shoreline. Three to five sampling

locations will be positioned evenly spaced along each transect. Additional sampling locations will be

positioned between each transect and close to Outfall 013 and two sampling locations will be placed in the

wetland area for a total of 45 sampling locations within the Waterside Investigation Area. The exact

locations of the sampling locations may vary according to the conditions of the substrate, the nature of

depositional processes observed in the geophysical survey, and agency consultation prior to the field effort.

At each of the 45 sample locations, field measurements will be taken, surface sediment will be collected and

inspected, and sediment cores collected. Surface water samples will be collected at a sub-set of the

locations within the grid. The locations will be sampled using a motorized boat. While collecting the

sediments at each station, the boat will be anchored. The vessel will be mobilized in such a way as to

minimize the potential for disturbance of the sediment and surface water via wave or propeller action. A

differential global positioning system (DGPS) unit will be used to record all sample station coordinates to

sub-meter accuracy. The sampling program will include surface sediment samples and subsurface

Vibracore™ samples. While this sampling plan provides a framework for the proposed sampling approach,

field observations will determine the final sample selection and which samples are chosen for laboratory

analysis.

Ten (10) additional surface sediment and surface water sampling locations will be chosen up river, down

river, and across river from the site to provide additional background and baseline area-wide data. An effort

will be made to obtain background samples from locations with similar ecological parameters (e.g., sediment

grain size, water depth, flow regime, tidal influence, etc.) as those adjacent to the site.

As described in more detail below, the field activities for the Waterside investigation are as follows:

Bathymetric and utility survey;

Surface sediment sampling;

Subsurface sediment sampling using Vibracore™;

Surface water sampling; and


35

Laboratory testing including forensics evaluations.

A summary of the data types, quantities, analytes and methodologies, and data uses is presented in Table

6. Permits or access agreements that may be required from the District of Columbia, United States Coast

Guard (USCG), the USACE and the National Park Service (NPS) will be obtained prior to initiation of the

field program.

The following sections describe the field activities that will be performed during the Waterside investigation.

All of the sampling locations within the Waterside Investigation Area are presented in Figure 11. Additional

samples will be collected from the background sampling areas to be identified based on information in

Appendix C. Specific procedures for the field work are described in the SAP.

Phase I, Task 1: Bathymetric and Utility Surveys

Prior to initiation of any intrusive sediment sampling, a bathymetric and utility survey will be conducted in the

Waterside Investigation Area. The bathymetric survey will provide a basis for understanding the depth of

the water column and the configuration of the river bottom and will be used to prepare a contour map of the

top of the sediment surface in and around the investigation areas. The utility survey will be conducted to

identify river bottom pipelines, cables and lines that may be located in the planned area of investigation.

Their presence and global positioning system (GPS) benchmarked locations will be noted on a base map of

the area.

A specialty subcontractor will perform the utility survey within the Waterside Investigation Area identified in

Figure 11. A limited bathymetric survey will also be performed at background sampling locations to assure

the similarity of river bottom morphology with that at the site and to confirm the lack of utility crossings at

these locations. Side scan sonar and/or magnetometer surveys will be used to identify any utilities or large

pieces of debris that might interfere with the proposed sampling activities.

It is anticipated that parallel survey lines will be run at 50-foot intervals throughout the survey area.

Additional tie lines will be run perpendicular to these lines. The contractor will use a survey-grade precision

fathometer (Odom Hydrotrack Fathometer or equivalent) to collect continuous water depth data along the

track lines. The contractor will continuously log each geographic position (X-Y location) using DGPS.

Depth and geographic location will be sent to the survey computer using the Integrated Survey Software

package. Time will be continuously recorded; therefore, tidal correction will be available for post-processing

using data from a tide gage that will be installed and surveyed prior to the bathymetric survey. Survey

accuracy will follow the USACE Manual No. 1110-2-1003 for hydrographic surveying (USACE, 2002).


36

Phase II, Task 1: Surface Water Sampling

Surface water sampling will be conducted prior to sediment sampling to assure the integrity and

representative nature of the sample. A total of twenty (20) water samples will be collected from immediately

above the sediment-water interface in order to capture potential impacts of groundwater discharge. Ten

(10) samples will be collected from within the Waterside Investigation Area and ten (10) samples will be

collected from background sampling locations.

The sampling boat will be located above the selected sampling location using GPS coordinates. Upon

arrival at each sampling station, a depth-to-sediment measurement will be collected to record the water

depth. The water depth will be recorded with an accuracy of ±0.1 feet. Two sets of field measurements of

water quality will be taken at each station. One measurement will be taken near the water surface,

approximately one foot below the water surface, and a second measurement within one foot from the top of

the sediment surface. Only one water quality measurement will be taken at mid-water depth and at stations

where the water depth is less than three feet. The water quality parameters to be measured in the field

include the following:

Temperature (degrees Celsius, °C);

Dissolved Oxygen (milligrams per liter, mg/L);

pH (standard units, S.U.);

Turbidity (Nephelometric Turbidity Units NTU); and

Conductivity (micromhos per centimeter, µmhos/cm).

The surface water sample for chemical analysis will be obtained from approximately one foot above the

sediment-water interface using a depth specific sampling device. The water samples will immediately be

packaged for shipment to the laboratory following preservation and management protocols described in the

accompanying SAP.

Surface water samples will be analyzed for the following parameters:

In all samples – Total and dissolved phase metals, PCB aroclors, PAH16, and hardness.

In a sub-set of up to 10 samples - VOCs, SVOC, pesticides, dioxins/furans.

A summary of the analytes and methodologies is presented in Table 6 and details on chemical analyses are

provided in the SAP.


37

Phase II, Task 3: Surface Sediment Samples

The sediment sampling activities outlined below will conform to U.S. USEPA and ASTM standard methods

where appropriate (ASTM, 2000a; ASTM, 2000b; U.S. USEPA, 2001).

A surface sediment grab sample will be collected at all 45 of the sampling locations shown in Figure 11, in

addition to 10 background locations (total of 55 surface sediment samples). If obstructions such as boulders

or cobbles are encountered at a specific station, the location of the station may be changed to collect

sediment samples as required. In the case that boulders or debris are encountered, samples will be

collected as close as possible to the specified sample location.

All surface sediment samples will be collected from a depth of 0 to 6 inches below sediment surface with a

Petite Ponar grab sampler or the equivalent. During this phase of work, the surface samples will be logged

for visual and physical observations. A portion of the sample will be placed in a pan, inspected for sediment

type, color, odor, obvious signs of biota and other notable features, and then returned to the river. The

remainder of the sample will then be prepared for shipment to the laboratory.

Field personnel will record field observations of the physical characteristics of the sediment encountered at

each sampling station and also important observations regarding the physical characteristics of the study

area. Information recorded will include:

Sample station designation;

Presence of fill material, coal or coke, or asphalt- or tar-like materials;

Presence or absence of aquatic vegetation;

Sediment color, texture, and particle size; and

Odor and presence of sheens or LNAPL and/or DNAPL.

The 55 surface sediment samples used for chemical testing will be processed by personnel in the field. The

samples will be screened using a PID and oversized material such as twigs, shells, leaves, stones, pieces of

wood, and vegetation will be removed by hand. The grab sample will be removed from the sampling device

using a stainless steel spoon/scoop and placed in a decontaminated 1-gallon stainless steel or Pyrex glass

mixing bowl. Each sample will be visually examined for physical characteristics such as composition,

layering, odor, and discoloration. Samples for VOC, Simultaneously Extracted Metals (SEM), and acid

volatile sulfide (AVS) analyses will be collected prior to sediment homogenization. The remaining sample

will be homogenized in the mixing bowl and placed in appropriate sample containers. Sediment sampling

equipment such as bowls, spoons, augers, and dredges will be decontaminated prior to and following


38

sample collection as described in the accompanying SAP. Each jar will be properly labeled with the name

of the study site, the station location designation, the time of collection, the date of collection, and name of

collector. Following sample preparation, glass jars will be kept at 4ºC. Surface sediment samples will be

analyzed for the following parameters:

In all samples – Total Organic Carbon (TOC), grain size, metals, SEM and AVS, PCB aroclors, and

PAH16.

In a sub-set of up to 20 samples - VOCs, SVOC, pesticides, dioxins/furans.


provided in the SAP.

Phase II, Task 4: Subsurface Sediment Samples/Vibracore™ Borings

Forty-five Vibracore™ sediment borings will be completed at the sediment sampling locations shown on

Figure 11 (i.e., co-located with the surface sediment sampling locations). The sediment cores will be

collected using a small boat equipped to advance a 3-inch diameter Vibracore™ sampler to a maximum

depth of 10 feet below the sediment surface, or to refusal, whichever is encountered first. The ten foot

target depth is based on published average sedimentation rates for the Anacostia River (approximately 4 to

6.5 cm/yr) and should provide a sediment column that includes sedimentation which generally predates the

operation of the facility. A second consideration is the general limits of the Vibracore™ sampling tool which

vary depending on sediment type and compaction history.

To meet the objectives for this task, the sampling will be performed as follows:

The core sampler, equipped with a plastic liner, will be driven and extracted at each of the

designated sample locations;

The core liner will be extracted from the core barrel and split open;

The sediment sample will be screened for organic vapors with a PID and logged for physical

characteristics; and

Samples from up to three horizons within each core will be collected.

It is estimated that up to 165 discrete interval subsurface sediment samples will be collected for laboratory

analysis from the 45 sampling locations in the Waterside Investigation Area and the 10 background

locations (3 horizons at 55 locations). Subsurface sediment samples will be analyzed for the following

parameters:


39

In all samples - PCB aroclors (performed using an on-site lab), and PAH16;

In a sub-set of up to 20 samples – TOC and grain size; and

In a sub-set of up to 7 samples – forensic testing to evaluate PCB and PAH origins and

contributions.

These data will establish a database from which to further evaluate the horizontal and vertical extent of PCB

and PAH constituents in river sediments adjacent to the Benning Road facility. Visually-impacted zones will

be logged and the PCB data will help to define impacted areas of concern, concentration gradients, and

sediment quality data gaps, if they exist. These data will serve as the basis from which to refine potential

future sampling events.


provided in the SAP. The Waterside sampling program will include the collection of up to seven (7)

sediment samples for submittal to a specialty forensics laboratory for fingerprinting purposes. Testing will

be performed to identify PCBs and PAH contributors to the total PCB and PAH load identified in the

samples. Testing may also include upstream (i.e., background) samples, if field observations indicate an

alternative potential source of PCBs and PAHs that warrants further consideration. This forensic analysis

will be used to differentiate between Benning Road sources and other potential sources of PCBs and PAHs

in the Anacostia River sediments.

5.2.3 Investigation-Derived Waste (IDW) Management

IDW generated during the Landside and Waterside investigations include the following:

Disposable material such as Geoprobe®/Vibracore™ liners, personal protective equipment (PPE),

plastic sheeting, etc.

Drill cuttings

Excess soil/sediment leftover from sampling activities

Well development water

Purge water

Decontamination water

Minimally-contaminated disposable sampling materials and PPE will be rinsed and disposed of as ordinary

solid waste. Drill cuttings, soil and sediment will be containerized and sampled for RCRA waste

characteristics and PCBs. These wastes will be managed as dictated by the waste characterization results

and disposed of at properly permitted off-site disposal facilities. All water will be containerized, sampled and

disposed of at a permitted off-site facility.


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5.3 Data Evaluation and Validation

All laboratory analytical data will be provided by the supporting laboratories in electronic formats, both

Portable Document Format (PDF) and electronic data deliverables (EDD). The PDF format deliverable will

include both sample results and all quality control (QC) results in standardized CLP-like format, as well as all

supporting raw data. The PDF report will be searchable (embedded text) and bookmarked to facilitate data

review. The associated EDD will be provided in an EQuIS four-file format. AECOM’s requirements and

clarifying definitions and valid values file for the EQuIS four-file format will be provided to all supporting

laboratories. Complete paginated data packages will contain the following minimum information:

A narrative specific to the sample data group (SDG) addressing any difficulties encountered during

sample analysis and a discussion of any exceedances in the laboratory quality control sample

results;

A cross-referenced table of field and laboratory identification numbers;

Analytical and preparatory method references;

Definition of any data flags or qualifiers used; a list of valid data flags and qualifiers for use in the

EQuIS reporting format will be provided;

A table of contents for the data package similar to the USEPA Complete Sample Delivery Group

File (CSF) Audit Checklist;

A chain-of-custody signed and dated by the laboratory to indicate sample receipt. The temperature

of the cooler will be noted on the chain-of-custody. Copies of shipping air bills will also be provided;

Results for each field sample, blank and QC sample in units appropriate to the method presented

on Form 1s or equivalent; reporting limits will also be provided and any analyte which is not

detected will be reported as less than the reporting limit.

Dilution factors for each sample or analyte;

Calibration data including raw data; initial calibration curve data such as linear regression statistics

or average relative response factors and percent relative standard deviation; continuing calibration

data such as relative response factors and percent difference data;


41

Gas chromatography/mass spectrometry (GC/MS) and Inductively Coupled Plasma-Mass

Spectrometry (ICPMS) tuning data;

Internal standard data;

Surrogate (system monitoring) data;

Inductively Coupled Plasma (ICP) inter-element correction factors, linear range data, serial dilution

data, and interference check sample results;

Copies of laboratory notebook pages or preparation logs showing sample preparation

documentation;

Field sample results and raw data (chromatograms, ICP printouts, etc.) including dilution data;

Laboratory QC data including method blank data, laboratory duplicate data reported as relative

percent difference (RPD), laboratory control spike data, reported as percent recovery; MS/MSD

data reported as percent recovery with RPD calculated; all associated raw data will also be

provided;

Copies of phone logs, faxes and e-mails associated with the sample set; and

Any other data necessary to conclusively confirm the analytical results reported and the overall

quality of the data.

The laboratory will retain a copy of the completed data package and all copies of laboratory results,

laboratory notes, quality assurance/quality control (QA/QC) data, and chain-of-custody record for a period of

10 years unless a shorter retention period is agreed upon in writing. All raw data on magnetic media along

with identifying information will be retained for the duration of the Consent Decree and for a minimum period

of 6 years after its termination.

Upon receipt from the laboratory, hard copy data and EDDs will be checked for completeness. During the

data analysis process, a variety of quality checks are performed to ensure data integrity. These checks

include:

Audits to ensure that laboratories reported all requested analyses;

Checks that all analytes are consistently and correctly identified;


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Reviews to ensure that units of measurement are provided and are consistent;

Reports to review sample definitions (depths, dates, locations); and

Proofing manually entered data against the hard-copy original.

All data generated from activities under this workplan will be subjected to assessment of data quality and

usability per methodology provided in the QAPP. This assessment will include limited or full validation in

accordance with USEPA National Functional Guidelines. Data qualifiers consistent with USEPA guidelines

will be applied to results in the database. Reconciliation with the project data quality objectives will be

performed and results of this assessment will be included in the RI report. Factors to be considered in this

assessment of field and laboratory data will include, but not necessarily be limited to, the following:

Conformance to the field methodologies and standard operating procedures (SOPs) proposed in

the Work Plan and QAPP;

Conformance to the analytical methodologies provided in the QAPP;

Adherence to proposed sampling strategy;

Presence of elevated detection limits due to matrix interferences or contaminants present at high

concentrations;

Unusable data sets (qualified as “R”) based on data validation;

Data sets identified as usable for limited purposes (qualified as “J”) based on data validation;

Effect of qualifiers applied as a result of data review on the ability to implement the project decision

rules; and

Status of all issues requiring corrective action, as presented in the QA reports to management.

The effect of nonconformance (procedures or requirements) or noncompliant data on project objectives will

be evaluated. Minor deviations from approved field and laboratory procedures and sampling approach will

likely not affect the adequacy of the data as a whole in meeting the project objectives. The assessment will

also entail the identification of any remaining data gaps and an assessment of the need to re-evaluate

project decision rules. This assessment will be performed by the AECOM technical team, in conjunction

with the AECOM Project QA Officer, and the results presented and discussed in detail in the final report.


43

5.3.1 Data Management

Due to the dynamic nature of this investigation, data management will be critical to the success of the

assessment.Automation of data collection, transmission, and processing will be integral to the performance

of the project.

5.3.2 Field Data Collection and Transmission

Each investigation point will be located using a global positioning system receiver with sub-two-meter

accuracy.These data will be uploaded on a daily basis to the project database that is discussed below in

Section 5.3.4. Based on accessibility, exterior locations will also be surveyed by a licensed surveyor, while

locations in building interiors will be field-measured from known landmarks.

Field notes will be transmitted to the project team in a timely manner. Laboratory deliverables will be

provided in a format ready for upload into the project database.

5.3.3 Data Review

Field notes will be reviewed against the laboratory chains-of-custody.Field notes and field forms will be

reviewed by the field team leader for accuracy and completeness.

At the beginning of each day of field work, a summary of anticipated laboratory deliverables for the day will

be prepared. At the end of each day, the project team will review the list of daily deliverables for

completeness and evaluate analytical data against applicable regulatory criteria. Analytical data will be

reviewed and validated as described in the QAPP.

5.3.4 Project Database

Field data, laboratory data, and geospatial data will be uploaded to and stored in the project database.

Laboratory deliverables will be received in an AECOM-specified electronic format ready for upload to the

EQuIS database, and the database will be used with a GIS to prepare figures for evaluation of impacts and

data gaps, while the field program is ongoing.

5.4 Risk Analysis

The RI will include performance of a Human Health and Ecological Risk Assessments (ERA) using validated

data obtained during the RI field investigation. The approaches for both the Human Health and the

Ecological Risk Assessments are summarized in the following sections and presented in detail in

Appendices D and E, respectively.


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5.4.1 Human Health Risk Assessment

A baseline Human Health Risk Assessment (HHRA) will be conducted to evaluate potential human health

risks at the Siteusing the four step paradigm as identified by the USEPA in the Risk Assessment Guidance

for Superfund, Volume I – Human Health Evaluation Manual (USEPA, 1989a). The steps are:

Data Evaluation and Hazard Identification;

Dose-Response Assessment;

Exposure Assessment; and

Risk Characterization.

As discussed in Section 3.1 above, direct or indirect exposure pathways on the Landside portion of the Site

are determined to be incomplete or insignificant because:

Access to the Landside portions of the Site is limited by perimeter fencing and tight 7 day/24 hour

security;

The presence of impervious surfaces preventing contact with surface soil;

Contact with subsurface soil is restricted by HASP procedures to prevent or manage worker’s

exposure during excavation activities; and

Groundwater is not used as a local source of drinking water.

The HHRA therefore will focus on potential human health exposures to Anacostia River surface water,

sediments, and fish. Because contaminant migration pathways via overland flow through storm drains and

groundwater discharges to the Anacostia River may be of concern, the HHRA also will include evaluation of

groundwater (as it discharges to the surface water of the Anacostia River).

The HHRA work plan is organized into the following sections:

Data Evaluation and Hazard Identification – presents the methods to be used in the data evaluation

and hazard identification, including selection of COPCs that will be evaluated quantitatively in the

risk assessment;

Dose-Response Assessment – presents a discussion of the dose-response assessment process.

The dose-response assessment evaluates the relationship between the magnitude of exposure

(dose) and the potential for occurrence of specific health effects (response) for each COPC. Both

potential carcinogenic and non-carcinogenic effects will be considered. The most current USEPA-

verified dose-response values will be used when available;


45

Exposure Assessment - presents a discussion of the exposure assessment process. The purpose

of the exposure assessment is to provide a quantitative estimate of the magnitude and frequency of

potential exposure to COPCs by a receptor. Potentially exposed individuals, and the pathways

through which those individuals may be exposed to COPCs are identified based on the physical

characteristics of the Study Area, as well as the current and reasonably foreseeable future uses of

the Study Area. The extent of a receptor's exposure is estimated by constructing exposure

scenarios that describe the potential pathways of exposure to COPCs and the activities and

behaviors of individuals that might lead to contact with COPCs in the environment. For the

Waterside, thefollowing potentially complete exposure scenarios are identified as warranting

evaluation:

Worker – potential direct exposure to site-related COPCs in surface water and sediment

while working along the banks of the Anacostia River adjacent to the Site;

Recreational Receptor – potential direct exposure to site-related COPCs in surface water

and sediment while wading or swimming in the Anacostia River adjacent to the Site;

Recreational Angler -potential indirect (consumption) exposure to site-related COPCs that

may have bio-accumulated into fish in the Anacostia River, and to COPCs in surface water

and sediment while fishing in the river.

Despite the presence of an advisory warning against the consumption of certain species of fish from

the Anacostia and Potomac Rivers, it will be assumed that a recreational angler visits the Anacostia

River to fish and consumes his/her catch;

Risk Characterization – presents a discussion of the risk characterization process and

uncertainties associated with the risk assessment process. Risk characterization combines

the results of the exposure assessment and the toxicity assessment to derive site-specific

estimates of potentially carcinogenic and non-carcinogenic risks resulting from both current

and reasonably foreseeable future potential human exposures to COPCs. The results of

the risk characterization will be used to identify constituents of concern (COCs), which are

the subset of those COPCs whose risks result in an exceedance of the target risk of 10-6 for

potential carcinogens and a target Hazard Index of 1 for non-carcinogens (that act on the

same target organ) (USEPA, 1990; 1991b);

Uncertainty Evaluation - Within any of the steps of the risk assessment process described

above, assumptions must be made due to a lack of absolute scientific knowledge. Some of

the assumptions are supported by considerable scientific evidence, while others have less


46

support. The assumptions that introduce the greatest amount of uncertainty in this risk

evaluation will be discussed in the Risk Characterization section of the HHRA report. The

potential contribution of background to Site-related risks will also be discussed; and

Summary and Conclusions - discusses the summary and conclusions section of the

baseline HHRA report.

5.4.2 Ecological Risk Assessment

The ecological risk assessment (ERA) will be conducted according to the general tiered approach and

methodology provided by the USEPA (1997, 1998, and 2001) based on the validated results of the

Waterside field investigation to evaluate the potential for ecological risks associated with exposure to

environmental media within or along the Anacostia River adjacent to the Site. The results of the ERA will be

used to help inform the need for any additional evaluation and/or remedial action at the Site, and the NRDA.

The ERA will focus on the Waterside portion of the Site, and will include evaluation of groundwater (as it

discharges to the surface water of the Anacostia River), surface water, and sediment.

The general tiered approach of the ERA includes three main components: Problem Formulation, Risk

Analysis, and Risk Characterization. Problem Formulation involves defining the objectives of the ERA and

formulating the plan for characterizing and analyzing risks based on available site-specific information on

stressors. Through this process, the CSM (Section 3) is better defined and potential exposure pathways,

ecological receptors, and risk assessment endpoints are identified.

The Risk Analysis phase involves the evaluation of data to characterize potential ecological exposures and

effects. Exposure point concentrations (EPCs) will be estimated for each COPC for each medium (e.g.,

sediment, surface water) to represent the concentrations that ecological receptors such as fish and benthic

invertebrates may encounter. EPCs will be compared to literature-derived toxicity thresholds for each

receptor to evaluate potential risks of COPC exposure in each type of media. Potential exposure of higher

trophic level wildlife receptors includes direct or indirect ingestion of surface water, sediment, and ingestion

of food items containing COPCs. Dietary doses of COPCs will be estimated for each wildlife receptor using

food web exposure models based on exposure assumption values (e.g., body weights, food and water

ingestion rates, relative consumption of food items, foraging range, exposure duration, etc.) and evaluated

by comparing to daily dietary dose toxicity reference values (TRVs).

For the Risk Characterization, the results of the risk analysis are interpreted to determine the significance of

any risks predicted for each assessment endpoint. This evaluation is based on the nature and magnitude

and spatial and temporal patterns of predicted effects. Comparisons to background or reference sites and


47

evaluation of the potential for recovery are also included in this analysis. The Risk Characterization

concludes with a summary of uncertainties associated with the risk assessment.

5.5 Remedial Investigation Report

Upon completion of field activities and receipt of the analytical data, a draft RI Report will be prepared for

submittal to DDOE. The draft report will be submitted to DDOE within 120 days of the completion of field

work as required by the Consent Decree. The report will include the following elements:

Site description;

Site history and previous investigations/remedial actions;

Description of field activities;

Results of field activities to determine physical characteristics (e.g., surface water hydrology,

geology/hydrogeology, ecology, etc.);

Nature and extent of contamination;

Contaminant fate and transport;

Results of the HHRA and ERA ;

Findings and conclusions; and

Recommendations.

A more detailed report outline is provided as Appendix F. Geologic logs, cross sections, aquifer test

results, laboratory data, validation reports, and pertinent field data logs will be included as appendices.

The draft RI Report is subject to review and approval by DDOE. DDOE also may solicit comments from

other regional and federal agencies. In addition, DDOE will make the draft RI Report available for public

review by posting on DDOE’s website for at least 30 days prior to approving the RI. Pepco will revise the

draft RI Report as appropriate to address comments from DDOE, other regulatory agencies, and the

public.Pepco will submit a final RI Report following regulatory review.

5.6 Feasibility Study

An FS will be conducted for the Study Area based on the results of the RI. The objectives of the FS are

to (a) identify remediation requirements and establish cleanup levels as necessary to eliminate or prevent

unacceptable risks to human health and the environment, and (b) identify, screen and evaluate potential

remedial alternatives. Various steps involved in the FS process are described in the following

paragraphs. An FS Work Plan Addendum will be submitted upon the evaluation of data obtained from the

RI field activities.


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5.6.1 Identification of Remediation Requirements and Establishment of RAOs

The FS will identify areas and volumes of media for which remediation is required either (a) to eliminate or

control conditions in the Anacostia River posing an unacceptable risk to human health and the

environment or (b) to prevent the migration of contaminant from the Site to the river that would cause or

contribute to an unacceptable risk to human health or the environment. All calculations related to area

and volume estimates will be documented in the FS Report. For the areas where a remediation

requirement is identified, remedial action objectives (RAOs) and preliminary remedial goals (PRGs) will

be developed in consultation with DDOE. The PRGs will be developed based on Site-specific risk factors.

The FS Report will describe the rationale for any cleanup levels established.

5.6.2 Development and Screening of Remedial Alternatives

The FS will identify and screen a focused set of technologies that have the potential to achieve the RAOs.

This step will follow USEPA presumptive remedy guidance and USEPA’s Contaminated Sediment

Remediation Guidance for Hazardous Waste Sites (2005). The FS will develop general response actions

(such as containment, treatment, excavation, pumping, institutional controls (e.g., deed restrictions),

engineering controls (e.g., encapsulation), or other actions, singly or in combination) for each medium of

interest (e.g., soil, sediment, surface water, groundwater) to achieve RAOs, and will identify and evaluate

technologies applicable to each general response action to eliminate those that cannot be implemented at

the Site. Consistent with USEPA guidance, the range of remedial options to be considered will include, at a

minimum (a) alternatives in which treatment is used to reduce the toxicity, mobility or volume of

contaminants, (b) alternatives that involve containment with little or no treatment, and (c) a no-action

alternative. Screening of technologies will be based on effectiveness, implementability, and relative cost.

Technologies retained after the screening process will be assembled into alternatives for each remediation

area.

5.6.3 Treatability Studies

Treatability studies will be performed as necessary to assist in the detailed analysis of alternatives.

Treatability studies are generally performed to determine the effectiveness of a technology in achieving

the targeted cleanup levels, to obtain design parameters for a full-scale process, or to screen multiple

process options of a particular technology. Treatability studies are important when technologies have not

been sufficiently demonstrated or characterization data alone is insufficient to predict treatment

performance or to estimate the size and cost of treatment units. Treatability studies can be conducted on

a bench-scale in the laboratory or on a pilot-scale at the Site depending on the study objectives. The


49

need for treatability studies will be determined once the initial screening of technologies is completed and

sufficient data from the RI are available.

5.6.4 Detailed Analysis of Alternatives

A detailed analysis will be conducted for the alternatives that are retained after the screening analysis. This

detailed analysis will consist of an individual evaluation of each alternative against the following evaluation

criteria and a comparative evaluation of all options against the evaluation criteria with respect to one

another:

Overall protection of human health and the environment;

Compliance with applicable regulations;

Long-term effectiveness;

Reduction of toxicity, mobility, or volume through treatment;

Short-term effectiveness;

Implementability;

Cost;

DDOE acceptance; and

Community acceptance.

5.6.5 Feasibility Study Report

Upon completion of the detailed evaluation of alternatives, a draft FS Report will be prepared for submittal to

DDOE. The report will (a) document the location and extent of media requiring remediation and describe

the associated cleanup levels and RAOs, (b) describe the results of the identification and screening of

alternatives, and the detailed evaluation of alternatives, and (c) identify a preferred alternative for remedial

action.

5.6.6 Regulatory Review and Public Comment

The FS Report is subject to review and approval by DDOE. DDOE also may solicit comments from other

regional and federal agencies. In addition, DDOE will make the draft FS Report available for public review

by posting on DDOE’s website for at least 30 days prior to approving the FS Report. The FS Report will be

revised as appropriate to address comments from DDOE, other regulatory agencies, and the public.

Pepco will submit a final FS Report following regulatory review and public comment.


50

6 Project Organization

The RI/FS activities will be performed principally by AECOM (or its subcontractors) on behalf of Pepco.

The project will be overseen by the DDOE to ensure compliance with the Consent Decree requirements.

The Pepco Project Manager will maintain regulatory interface with DDOE and the AECOM Project

Manager will support the Pepco Project Manager as needed. The AECOM Project Manager may

interface directly with DDOE on technical matters related to the project. Roles and contacts for various

project personnel are summarized in Table 7. Responsibilities for key project personnel are described in

the following paragraphs:

Pepco Project Manager

Ms. Fariba Mahvi will serve as the Pepco Project Manager. Ms. Mahvi’s responsibilities include:

Representing Pepco management,

Reviewing AECOM’s work;

Primary interface with DDOE,

Securing project funding,

Working with Pepco Community Involvement Coordinator (Donna Cooper) to implement CIP, and

Reviewing all project documents before submission to DDOE.

AECOM Project Manager

The AECOM Project Manager, Mr. Ravi Damera, has responsibility for day-to-day management of

technical and scheduling matters related to the project. Other duties, as necessary, of the AECOM

Project Manager include:

Subcontractor procurement,

Assignment of duties to project staff and orientation of the staff to the specific needs and

requirements of the project,

Ensuring that data assessment activities are conducted in accordance with the QAPP,

Approval of project-specific procedures and internally prepared plans, drawings, and reports,


51

Serving as the focus for coordination of all field and laboratory task activities, communications,

reports, and technical reviews, and other support functions, and facilitating site activities with the

technical requirements of the project, and

Maintenance of the project files.

AECOM Technical Leaders

The AECOM Project Manager will be assisted by Technical Leads, whose duties will include:

Ensuring data assessment activities are conducted in accordance with the QAPP,



technical requirements of the project,

Technical review and/or approval of project-specific procedures and internally prepared plans,

drawings, and reports,



technical requirements of the project, and

Maintenance of the project files.

AECOM Project QA officer

The AECOM Project QA Officer, Mr. Gary Grinstead, has overall responsibility for quality assurance

oversight. The AECOM Project QA Officer communicates directly to the AECOM Project Manager.

Specific responsibilities of the AECOM Project QA Officer include:

Preparing the QAPP,

Reviewing and approving QA procedures, including any modifications to existing approved

procedures,

Ensuring that QA audits of the various phases of the project are conducted as required,

Providing QA technical assistance to project staff, and

Ensuring that data validation/data assessment is conducted in accordance with the QAPP.


52

AECOM Analytical Task Manager

The AECOM Project Chemist/Laboratory Coordinator, Mr. Robert Kennedy, will be responsible for

managing the subcontractor laboratories, serving as the liaison between field, laboratory personnel, data

validation and database teams and assessing the quality of the analytical data.

AECOM Health and Safety Officer

The AECOM Project Health and Safety Officer, Mr. Sean Liddy, will serve as a health and safety advisor

to the Project Manager and AECOM staff including:

Reviewing and approving Health and Safety Plans,

Reviewing subcontractor safety records,

Conducting safety audits,

Recommending appropriate PPE to protect AECOM personnel from potential hazards, and

Conducting accident investigations.

AECOM Field Team leader

The AECOM Field Team Leader, Mr. Scott Beatson, has overall responsibility for completion of all field

activities in accordance with the QAPP and is the communication link between AECOM project

management and the field team. Specific responsibilities of the AECOM Field Team Leader include:

Coordinating activities at the site,

Assigning specific duties to field team members,

Mobilizing and demobilizing of the field team and subcontractors to and from the site,

Directing the activities of subcontractors on site,

Resolving any logistical problems that could potentially hinder field activities, such as equipment

malfunctions or availability, personnel conflicts, or weather dependent working conditions,

Implementing field QC including issuance and tracking of measurement and test equipment; the

proper labeling, handling, storage, shipping, and chain-of-custody procedures used at the time of

sampling; and control and collection of all field documentation, and


53

Communicating any nonconformances or potential data quality issues to AECOM project

management.

AECOM Field Staff

The field staff reports directly to the AECOM Field Team Leader, although the Field Team Leader in some

cases will be conducting the duties of the field staff listed below. The responsibilities of the field team

include:

Collecting samples, conducting field measurements, and decontaminating equipment according

to documented procedures stated in the QAPP,

Ensuring that field instruments are properly operated, calibrated, and maintained, and that

adequate documentation is kept for all instruments,

Collecting the required QC samples and thoroughly documenting QC sample collection,

Ensuring that field documentation and data are complete and accurate, and

Documenting and communicating any nonconformance or potential data quality issues to the

AECOM Field Team Leader.

AECOM Subcontractors

AECOM specialty subcontractors may include, but are not limited to, drilling, surveying, analytical

laboratories, waste management, and equipment rentals. These subcontractors will work under the direct

supervision of AECOM field staff to carry out specific scope requirements.


54

7 Schedule

A tentative project schedule has been prepared (Figure 12) showing the duration of various tasks that will

be triggered by the approval of this work plan and associated SAP and HASP. The task durations

correspond to the deadlines specified in the Consent Decree. This schedule will be revised with actual

calendar dates upon the final approval of the work plans.


55

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AMEC. 2012. Benning Generation Station – 2011 Annual report for the TMDL Implementation Plan and the

PCB and Iron Source Tracking and Pollutant Minimization Plans. January 27, 2012

Anacostia Restoration Potential Workgroup (ARPW). 2009. Annual Report Card.

Anacostia Watershed Toxics Alliance (AWTA). 2009. White Paper on PCB and PAH Contaminated

Sediment in the Anacostia River. DRAFT FINAL. Anacostia Watershed Toxics Alliance. February 23, 2009.

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Cleaves, E, Edwards J., and K. Weaver, 1968. Geologic Map of Maryland, Maryland Geologic Survey,

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Doelling-Brown, P. 2001. Trophic transfer of PCBs in the food web of the Anacostia River. PhD.

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Technologies, Anacostia River, Washington, DC.

Interstate Commission on the Potomac River Basin (ICPRB). 2007. Total Maximum Daily Loads of

Polychlorinated Biphenyls (PCBs) for Tidal Portions of the Potomac and Anacostia Rivers in the District of

Columbia, Maryland, and Virginia. September 28, 2007.

Jacques Whitford Company, Inc. 2003. Salvage Yard Soil Investigation, Benning Service Center.

Washington, DC.

Katz, C.N., A.R. Carlson and D.B. Chadwick. 2001. Draft Anacostia River Seepage and Pore water Survey

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Environment.http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Documents/www.

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August 11, 2011.

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Environment.http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Pages/citizensinfo

center/fishandshellfish/index.aspx. Last updated: September 20, 2011.

Maryland Department of the Environment (MDE). 2012. Database query for contaminant concentrations in

fish tissue collected from the Anacostia River, 2002 to 2010. John Hill, Environmental Specialist, Maryland

Department of Environment. May 21, 2012.

Metropolitan Washington Council of Governments (MWCG). 2007. Anacostia River Watershed:

Environmental Condition and Restoration Overview. DRAFT. March 2007.

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Relevant to Potential Contaminants of Concern within the Anacostia River Watershed. National Oceanic

and Atmospheric Administration. Coastal Protection and Restoration Division. June, 2000.

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NE Washington, DC. Ecology & Environment, Inc. April 2001.

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Washington, DC. Ecology & Environment, Inc. June 2008.

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Pepco. 1991. Benning Generating Station PCB Leaking Capacitor Cleanup Report.

Pepco. 1995. Benning Generating Station PCB Cleanup Report.

Pepco. 1988. Benning Substation # 7 Parking Area Cleanup Report.

http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Documents/www.mde.state.md.us/assets/document/Anacostia%20Advisories%20for%20MD%20Portion.pdf

http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Documents/www.mde.state.md.us/assets/document/Anacostia%20Advisories%20for%20MD%20Portion.pdf

http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Pages/citizensinfocenter/fishandshellfish/index.aspx

http://www.mde.state.md.us/programs/Marylander/CitizensInfoCenterHome/Pages/citizensinfocenter/fishandshellfish/index.aspx


58

Pepco. 1996 through 1997. Benning Wetland PCB Data.

Pinkney, A.E., C.A. Dobony and P. Doelling Brown 2001a. Analysis of contaminant concentrations in fish

tissue collected from the waters of the District of Columbia. U.S. Fish and Wildlife Service, Chesapeake

Bay Field Office, Annapolis, MD CBFO-C01-01b.

Scatena, F.N. 1987. Sediment Budgets and Delivery in a Suburban Watershed: Anacostia Watershed.,

Ph.D. Dissertation; Johns Hopkins University, Baltimore, MD.

Sullivan, M.P. and W.E. Brown, 1988. The tidal Anacostia model-Documentation of the hydrodynamics and

water quality parameters. Prepared for the DC Dept. of Consumer and Reg. Affairs by the Metropolitan

Washington Council of Governments, Washington, DC.

USACE Baltimore District, June 2007. Condition Survey, Anacostia River Basin, Washington, DC and

Maryland.

USACE, 2002. Engineering and Design - Hydrographic Surveying. EM 1110-2-1003. United States Army

Corps of Engineers, Washington, DC

URS. 1999. Phase I Environmental Site Assessment of the Benning Generating Facility, Washington, DC

USEPA, 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA.

U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Office of

Emergency and Remedial Response. USEPA 540/G-89/004. October 1988.

USEPA, 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and

Conducting Ecological Risk Assessments (Interim Final). U.S. Environmental Protection Agency, Office of

Solid Waste and Emergency Response, Office of Emergency and Remedial Response. USEPA 540/R-

97/006. June 1997.

USEPA. 1997. Multi-Media Inspection Report, Pepco, Benning Road Generating Station, Washington, DC

USEPA, 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum. U.S. Environmental

Protection Agency; Washington, DC USEPA/630/R-95/002F. April 1998.

USEPA, 2001. The Role of Screening-Level Risk Assessments and Refining Contaminants of Concern in

Baseline Ecological Risk Assessments. ECO UPDATE. Interim Bulletin Number 12. U.S. Environmental

Protection Agency, Office of Solid Waste and Emergency Response.


59

USEPA. 2009. Final Site Inspection Report for the Pepco Benning Road Site, Washington, DC

USGS. 2002. Lithologic Coring in the Lower Anacostia Tidal Watershed, Washington, DC Report 03-318.

Vokes, H. and J. Edwards, 1957. Geography and Geology of Maryland, Maryland Geologic Survey,

Baltimore Maryland, Bulletin 19

Velinsky, D. and J. Ashley. 2001. Sediment Transport: Additional Chemical Analysis Study, Phase II. Final

Report. Report No. 01-30. December 20, 2001.

Velinsky, D.J. and J.D. Cummins. 1994. Distribution of Chemical Contaminants in Wild Fish Species in

Washington, DC, Interstate Commission on the Potomac River Basin Report # 94-1, Rockville, MD.

Velinsky, D.J. and J. Cummins. 1996. Distribution of chemical contaminants in 1993-1995 wild fish species

in the District of Columbia. Interstate Commission on the Potomac River Basin, Rockville, MD.

Velinsky, D.J., G.F. Reidel, J. Ashley and J.C. Cornwell. 2011. Historical Contamination of the Anacostia

River, Washington, DC Academy of Natural Sciences, Philadelphia, PA.

Velinsky, D.J., G.F. Reidel and G.D. Foster. 1999. Effects of storm water runoff on the water quality of the

tidal Anacostia River. Academy of Natural Sciences, Philadelphia, PA.

Figures

Site Location

Site Location MapBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

1FIGURE

Source:USGS 7.5 Minute Topographic MapWashington East Quadrangle

BE

NN

ING

RO

AD

NE

FOOTE ST N

E

ROOSEVELT P

L NE

GRANT PL N

EGRANT P

L NE

HAYES ST NEANACOSTIA FREEW

AY

KENILWORTH

TERRACE NE

PARKSIDE PL NE

BURNHAM PL N

E

CASSELL PL NE

BARNES ST NE

ANACOSTIA AVE NE

JAY ST NE

ANACOSTIA RIVER

LANGSTON GOLF COURSE

KINGMAN LAKE

OUTFALL 013

36TH ST NE

EAD

S S

T N

E

34TH ST NE

ANACOSTIA AVE NE

AN

AC

OSTIA A

VE NE

BE

NN

ING

RO

ADB

RID

GE

BENNING ROADFACILITY (PEPCO)

NATIONAL PARK SERVICEKENILWORTH MAINTENANCE YARD

D.C. DEPARTMENT OF PUBLIC WORKSSOLID WASTE TRANSFER STATION

ANACOSTIA RIVER

PROPOSED INVESTIGATION AREA

BENNING ROAD FACILITYPROPERTY BOUNDARY

PROPERTY BOUNDARY

LEGEND:

Site PlanBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

2FIGURE

And Investigation Areas

RI/FS ProcessBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

3FIGURE

From:Consent DecreeRI/FS Scope of Work

Remedial Investigation

Work Plans andPermits

Collect andEvaluate Data

(Phased Approach)

Risk Analysis

RemedialInvestigation

Report

To:Remedy SelectionRecord of DecisionRemedial DesignRemedial Action

Feasibility Study

Identify and ScreenTechnologies

EstablishRemediation Goals

Feasibility StudyReport

Assemble andEvaluate

Alternatives

Site Vicinity MapBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

4FIGURE

C r y

s t

a l l

i n e

R

o c

k s

P a

t u x

e n

t

F o

r m a

t i o

n

A r u

n d

e l

C

l a y

P a

t a p

s c

o

F o

r m

a t

i o n

M a

g o

t h

y

Roc

kC

reek

Ana

cost

iaR

iver

Hen

son

Cre

ekC

amp

Spr

ings

D.C

. Mar

ylan

d

App

roxi

mat

e S

ite L

ocat

ion

Sea

Leve

l

-200

-400

-600

-800

-100

0

-120

0

-140

0

200

400

A l t i t u d e I n F e e t

*Hor

izon

tal S

cale

Exa

gger

ated

Sou

rce:

Mac

k, K

M. 1

966.

Gro

undw

ater

in P

rince

Geo

rges

Cou

nty,

Bul

letin

29:

Mar

ylan

d G

eolo

gica

l Sur

vey

Reg

iona

l Ge

olog

ic P

rofil

eB

enni

ng R

oad

Faci

lity

RI/F

S P

roje

ct34

00 B

enni

ng R

d., N

EW

ashi

ngto

n, D

C 2

0019

6FI

GUR

E

B

B'

A'

A

SB-4

SB-1SB-5

SB-3

SB-2

G&O-B-34

CTI-B-34CTI-B-12CTI-B-10

CTI-B-9 CTI-B-8CTI-B-7

GEO-B-2

GEO-B-4

GEO-B-1

GEO-B-8

GEO-B-5

GEO-B-6GEO-B-9

DCHP01

GEO-B-7

GEO-B-3

G&O-B-36

G&O-

G&O-B-37

CTI-B-3

CTI-B-4

CTI-B-5CTI-B-6

CTI-B-1

CTI-B-13

CTI-B-17

CTI-B-2

CTI-

CTI-B-16 CTI-B-14

B-15

B-38

G&O-B-18

BEN

NIN

G R

OA

D N

E

FOOTE ST NE

ROOSEVELT PL N

E

GRANT PL NE

GRANT PL NE

ANACOSTIA FREEWAY KENILWORTH TERRACE NE

PARKSIDE PL NE

BURNHAM PL NE

CASSELL PL N

E

BARNES ST NE

ANACOSTIA AVE NE

ANACOSTIA RIVER

LANGSTON GOLF COURSE

KINGMAN LAKE

36TH ST NE

EAD

S S

T N

E

34TH ST NE

ANACOSTIA AVE NE

AN

AC

OS

TIA AVE

NE

BEN

NIN

G R

D B

RID

GE

BENNING ROADFACILITY (PEPCO)

NATIONAL PARK SERVICEKENILWORTH MAINTENANCE YARD

D.C. DEPARTMENT OF PUBLIC WORKSSOLID WASTE TRANSFER STATION

ANACOSTIA RIVER

OUTFALL 013

PROPOSED INVESTIGATION AREA

BENNING ROAD FACILITYPROPERTY BOUNDARY

PROPERTY BOUNDARY

LEGEND:

APPROXIMATE LOCATION OF SOILBORING INSTALLED BY CTICONSULTANTS, INC. IN 2009

APPROXIMATE LOCATION OF SOILBORING INSTALLED BY GREENHOUSE &O'MARA, INC. IN 2009

USGS SOIL BORING DCHP01 INSTALLED IN 2002

APPROXIMATE LOCATION OF SOILBORING INSTALLED BYGEOMATRIX, INC. IN 1988

FIGURE 7

HISTORICAL AND PROPOSEDBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

LINE OF CROSS-SECTION

PROPOSED SOIL BORING

A A'

SOIL BORINGS

0 (MSL)

31

-64

0 (MSL)1.4

-64

G&

O-B

-34

GE

O-B

-7

GE

O-B

-9G

EO

-B-6

GE

O-B

-5

Out

fall

013

DC

HP

01

BSouth

B'North

Cross Section B-B'

3001500

10

20

Graphic ScaleNote:Depth to water of G&O-B-34taken 24 hours after drilling.

Mudflat

G&

O-B

-38

CTI

-B-6

CTI

-B-1

6

CTI

-B-3

G&

O-B

-36

GE

O B

-3

GE

O-B

-9

GE

O-B

-4

GE

O-B

-2

0 (MSL)

-56

38

-56

AEast

A'West

Anacostia Avenue

Cross Section A-A'

5002500

10

20

Graphic Scale

20

-20

-40

0 (MSL)

-20

-40

20

-20

-40

-60

-20

-40

-60

Geologic Cross SectionsBenning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

8FIGURE

Mean Sea Level

Depth To Water(Encountered during drilling.)

Depth To Water(Obtained from USGS.)

Stream Gauge(Taken at low tide fromUSGS Station 01651750)

Approximate Water Table

MSLB-3

8

Boring LocationAnd ID

Alluvium/Fill

Sand

Sand/Gravel

Clay, Silt, and SandIntermixed

Arundel Clay

Inferred Lithology

Legend:

Sou

rce

Are

aP

rimar

yS

ourc

esS

ourc

eM

edia

Rel

ease

Mec

hani

smE

xpos

ure

Med

ia

Pot

entia

lE

xpos

ure

Rou

te

Cur

rent

/Fu

ture

On-

Site

Wor

ker

Cur

rent

/Fu

ture

Con

stru

ctio

nW

orke

r

Cur

rent

/Fu

ture

Riv

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ecre

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Cur

rent

/Fu

ture

Rec

reat

iona

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r

Terr

estri

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lant

Com

mun

ity

Soi

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brat

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omm

unity

Ben

thic

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rtebr

ate

Com

mun

ity

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an a

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alia

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omm

uniti

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al In

gest

ion

Der

mal

/ D

irect

Con

tact

Inci

dent

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gest

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Der

mal

/ D

irect

Con

tact

Out

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latio

n

Indo

or A

ir(v

ia s

oil v

apor

)In

hala

tion

Inge

stio

n as

Drin

king

Wat

erD

erm

al /

Dire

ctC

onta

ct

Inci

dent

al In

gest

ion

Tren

ch A

irIn

hala

tion

Inci

dent

alIn

gest

ion

Der

mal

/ D

irect

Con

tact

Inci

dent

alIn

gest

ion

Der

mal

/ D

irect

Con

tact

Fish

Tiss

ueIn

gest

ion

Sur

face

Wat

er

Pot

entia

l Hum

an R

ecep

tors

/Exp

osur

e P

athw

ays

Pot

entia

l Eco

logi

cal R

ecep

tors

/Exp

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e P

athw

ays

Sur

face

Soi

l(0

-2 ft

bgs

)

Sub

surfa

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(2-1

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bgs)

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ater

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imen

t in

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ia

Pep

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oad

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lity

Six

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umen

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Bs.

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etal

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and

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from

form

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ater

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unof

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Vol

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Vol

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t/

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es:

ft bg

s - f

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gro

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surfa

ce.

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imen

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urfa

ceW

ater

Pot

entia

lly c

ompl

ete

path

way

.P

athw

ay c

onsi

dere

d to

be

inco

mpl

ete

or in

sign

ifica

nt.

Oth

er O

ff-S

iteS

ourc

es

Oth

er O

ff-S

iteS

ourc

es

Preliminary Conceptual Site Model Benning Road Facility RI/FS Project3400 Benning Rd., NEWashington, DC 20019

9 FIGURE

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